I think the whole Sherman with 75mm issue is pretty tricky and tends to get spun one way and then the next. I hope I'll be forgiven a somewhat long winded attempt to provide some general clarity:
The John Wayne Era
First of course there was the US legend of invincibility, with kind of an undertone of fear of the Tiger (especially) and the Panther that came down from the actual troops that had to face them. We know of course that the Tiger was very rare, and the Panther had it's problems, but the Panther actually did a great deal of the real damage. However so did the much more humble and less sexy Pz IVG, H or J and the various StuG III, especially on the defensive. and other Jagdpanzers like Jgpz IV, Hetzer etc.
The Panzer Leader Era
The wonderful Golden Age of Wargames of the 1960's and 1970s was somewhat influenced by post-war personal accounts and autobiographies of German fighter pilot, bomber, and tank aces, some of whom were still rather extreme nationalists to say the least (Rudel) while others who were much more reasonable still tended to exaggerate the Uber qualities of their kit and downplay the merits of their enemies, especially the Soviets. We have discussed this before in the context of books about WW2 fighters, and the legends about the experten ala Erich Hartmann, Joachim Marseille, Adolph Galland, Gunther Rall etc., but it also very much existed for tanks. Many Americans in particular developed a fetish for German tanks and a lot of the wargames from the Golden Age, ala squad leader etc. which were extremely influential to much later computer games in the 90's and oughts such as Close Combat, Steel Panthers, Combat Mission etc., tended to emphasize the heavy firepower and thick armor of late war German tanks over the merits of Allied armies such as air support, and Allied tanks like reliability, speed, fast turret traverse (for the Sherman), situational awarenes of the open turret US TD's, .50 cal machine guns, and even that wonky gyrostabilizer.
The Belton Cooper Era
Then we get the famous "Death Traps" book by Belton Cooper and Stephen Ambrose, emphasizing the counter-narrative that the Sherman was a piece of junk and literally a 'death trap'. Coopers job was more or less to hose out and fix blown up Sherman's and put them back in the line, which he noted sometimes meant putting completely untrained crews into the tanks who got blown up again with grim rapidity. To a large extent this was an attempt by Ambrose and some other historians to inject a little reality into the US perception of WW II (such as in the first ten minutes of Saving Private Ryan). Really commendable and it wasn't necessarily their fault that US pop culture and media kind of distorted the message.
None of that book is untrue but it does paint a somewhat slanted picture, due to his (Cooper's) perspective. The rather grim reality is that
most tank crews, German, British, Canadian, Russian, Free French or American, except maybe some of the elite Tigers, faced a
very dangerous job
if and when they actually got into a big battle with enemy tanks. If they were in a big tank battle quite often casualty rates were very high regardless, often reaching 90% or more. At El Alamein the British won but lost half of their tanks. In major battles like Kursk, Kharkov, Goodwood, Arracourt, in the Ardennes, Market Garden etc., tank casualties were horrendous. Tank crew like most WW2 soldiers involved at the tip of a spear, was almost a death sentence.
Wartime realities
Most of the time Allied tanks did
not face enemy tanks from 1944 onward. And if they didn't face enemy tanks, the survival rate for tank crews was actually much higher than infantry or other front line troops. Meanwhile in Sicily, Italy and North Africa, after the initial roughing up / panic at Kasserine Pass and subsequent reorganization, US forces found that if they had their act together they did not particularly need to fear German tanks. So they put their emphasis more on getting their act together with the kit they had rather than getting any new kit and having to make adjustments for that. The Pz IV's, StuG III etc. were vulnerable to the basic medium velocity
75mm M3 gun on the M4 Sherman, and the additional assets like still somewhat undersung Tank Destroyers, the (typically very good and efficient) US artillery support and Anglo-American air support, if used at peak efficiency, were sufficient to handle the bigger tanks like Tigers, Panthers and all the other big Jagdpanzers and so on. The 75mm in fact was considered so 'sufficient' that US field commanders very strenuously
resisted upgunning to the higher velocity 76mm gun, because it's HE shell was slightly less effective than the 75mm one and their most typical threat was still from AT guns and increasingly, panzerfausts. They also had little enthusiasm for the formidable
US 90mm M3 gun which could have been put into action on tanks and TD's sooner than it was.
It wasn't until after D-Day that they really began to have serious problems with the heavier German tanks and their very high velocity guns i.e. the
7.5 cm KwK 42 L/70 on the Panther and the
8.8 cm KwK 36 L/56 on the Tiger, which was bad enough to cause a scandal in the US and lead to extreme pressure on US military leadership to upgun and up-armor US armored vehicles. The British already had their firefly with the 17 pounder, an excellent gun though it's fitting in the M4 was somewhat less than ideal. Pressure on the US led to the faster rollout of improved US tanks, the addition of applique armor to US tanks in Europe, the production M4A3E8 and M3A3E2 "Jumbo" Sherman, and the 90mm gun armed M-36, and at the very end of the war, a few 90mm armed M-26 Pershings.
This had something to do with the terrain. North Africa was 'good' tank country in the sense that the ranges were very long, which favored the (higher velocity) German guns, however it was also not a great place for tanks to hide and by the time the Americans arrived the Allies were at least temporarily capable of seizing air superiority, and had a large number of well seasoned pilots doing relentless strikes. Big tanks (they did have some Tigers there) and 88 guns were prime targets for fighter bombers.
In Italy, it was better ground for defense but tanks in general had a hard time moving around. It was really more of a bloody infantry and artillery battle most of the time. Where tanks were significant such as at Anzio, once again Allied artillery and air support won the day, albeit after substantial losses.
In Western Europe with rolling hills, and a mix of open areas with forests, villages and hedgerows etc., it was very good
defensive tank country - with enough room to maneuver but also plenty of cover, and some of the heavier beast like tanks and tank killers brought over from the Russian Front took a deadly gruesome toll on Anglo-American forces, in spite of any design flaws they had.
World of Tanks Era
So now you have guys like
Major Nicholas Moran, the Irish born, American Army tank commander and historian who now works for World of Tanks franchise and does all these amusing viral videos and lectures about tanks. I kind of like the guy, and he knows a lot, but he definitely does have his biases (to be honest I think he has an anti-British bias among other things). To me the best things he does are the videos where he climbs inside almost every major tank of WW2 and shows you all the controls, systems and also design flaws that affected the crew. I think he and some other authors somewhat overstate the effectiveness of the M4 and understate it's flaws. Of course World of Tanks has many gung-ho Panzer lovers too, but it kind of carries it's own slightly off / reddit style Aspy junior gamer revisionism which I think distorts the picture quite a bit. You have some people now saying that the M4 was the best tank of the war and the PzKw V was a crappy tank. To me that is taking it way too far. Unlike the previous generation of semi-serious wargames like Close Combat or Combat Mission, which made some attempts at realism, the Free to Play World of Tanks is an arcade game which caters to whatever fantasies or delusions the kids want, - whatever it takes to get them to play, same of course with their equally dismal World of Warplanes which does it's best to spread distortions about WWII air combat. Whatever you want to say about older games like Il2, they at least made an effort toward realism.
Cold Rational Analysis / Threading the Needle
Wartime records like that wonderful document Fubar57 uploaded upthread paint a more nuanced picture. There certainly were severe massacres of Allied tank units at the hands of Tigers, Panthers, StuG III's and good old 88 flak / AT guns. But on the other hand you have major incidents like the
Battle of Arracourt where in somewhat foggy conditions, an American Armor division consisting almost entirely of 75mm gunned M4 Shermans, plus a few Tank Destroyers and some M7 'Priest' self propelled guns*, basically wiped out 114 Panthers for the loss of 25 tanks and 7 TD's. Part of the credit for this goes to the TD's, which as I said already I think are underrated. the super fast M-18 had a very good record, the M-36 Jackson could knock out most of the German heavy tanks at long range if they had the right ammunition, but even the more flawed / humble M-10 often did really well against German armor, particularly on the defense.
But a lot of the credit goes to the basic M4 / 75mm Sherman which when well led, could do real damage even in tank to tank warfare. Very similar things incidentally happened in Normandy. We all know the trouble Allied troops had in bocage country, but the Germans had the same trouble when they counter attacked in this era and as most are probably aware, with flank shots - that tend to be easier to achieve on the defensive - M4 /75mm Shermans could kill panthers with hits to their side armor, and Pz IV and StuG III etc. were basically dead meat.
When the M4 Sherman first came out, for all it's initial flaws, it was one of the best tanks in the world. It was a big help to the British and Commonwealth forces in 1942. Due to what you might call institutional complacency by the US military the basic design was only incrementally improved in 1943 and the first half of 1944. From the second half of 1944, there were bad massacres of US tanks, both in American and British hands, like at Goodwood and Market Garden etc., but there were also at least as many substantial victories like Arracourt which tended to be downplayed in the last 20-30 years. WW2 was a tough fight, the Germans were tough opponents, and their tanks were good. Meanwhile in Russia,
they actually liked the M4, which contrary to myth was a major improvement over the T-34/76 in almost every respect (including main gun and armor), and in fact it's only major flaw for them was the relatively narrow tracks and poor flotation, which meant due to their soggy ground it couldn't really be deployed except during the dry months. But when it was deployed by the Russians it was in elite guards units. This issue with the tracks was largely remedied in West Europe by the simple expedient of adding track extenders.
But the other part of it is more prosaic, from a variety of British and American studies both of WWII and Korea (where US M4 /76mm armed Sherman's faced off against Soviet made T-34 /85's) the deciding factor in tank warfare was surprise and situational awareness - i.e. the tanks that shot first usually won the engagement I think about 80% of the time. This in turn is partly why the oft criticized open top design feature of US Tank Destroyers may have actually been a stroke of genius, as for all it's many downsides it did contribute to enhanced Situational Awareness.
The very nature of tanks is at the center of the debate. Two contradictory things are both true, on the one hand the ideal job of the tank is to exploit disorganized enemy forces
after a breakthrough, to support infantry attacks and to drive around machine gunning and blasting demoralized enemy troops (but always with infantry support). But it's job was
also in practice to break through strong defenses (again with infantry and artillery - without infantry support tanks were and are very vulnerable) and to fight other tanks. The M4 was good at the first job and pretty good at the second, even with the 75mm gun. The ultimate WW2 version, the M4A3E8, usually with some enhanced armor (Patton had an extra 2" or 3" of armor cut off of knocked out American and even sometimes German tanks and welded to the fronts of his Shermans) and a relatively potent 76mm gun, was better in the latter job. But the reality is the Germans weren't able to field enough tanks after D-Day to require a better tank killer, and before D-Day the Americans' hadn't perceived a need for one (rightly or wrongly).
* there are some bizarre incidents in the battle such as a guy named
'Bazooka Charlie" Carpenter who took up an L-4 Cub aircraft with bazookas strapped to the wings and attacked columns of Panther tanks with it, supposedly killing two in a series of attacks.