Less then six months to collapse? You are underestimating the Japanese quite a bit. I believe Japan could have captured the entire Eastern maritime province, and the Soviets would not have been able to do anything about it until Germany was defeated at Berlin.
Okay...how are they going to achieve that? Have a glance at the map first before you say that. Also, remember that Vladivostock itself is a fortress no less formidable than Sevastopol, protected by Mountains and fortifications at the frontier that rival the maginot line. The Japanese army is outnumbered, outgunned and attacking in the teeth of the winter.
The eastern seaboard that you are referring to contains what??? Sakhalin, the port of Sovietskaya Gavan, a couple of fishing ports, and massive, trackless mountains behind that. They attack the eastern seaboard, take Sakhalin.....then what????
I believe that Vladivostock was essentially an impregnable fortress. It was immune to amphibious assault because of the defences, because of the beach types, and because of the currents . It was as least as impregnable as Sevastopol, and Truk, its only "weakness", if you could call it a weakness, was by landward assault.
Attacking Vladivostock has a near comparison in my opinion, the German assault onto Murmansk. The terrain is similalry devoid of communications, with the added complications of increased distance heavy vegetation and massive fortifications. The temperatures at Vladivostock are as extreme as they are in Murmansk (because of the effects off the gulf stream has on europe), and the distance to the objective many times that faced by the Germans in their assault on Murmansk. Yet you guys smooth over all of these issues, and glibly announce thaqt the Japanese can defeat the Russian in the blink of an eye. Dont forget, at the same time the Russians would be attacking along a front line which in its entirety stretches the same distance as the distance from Moscow to London, whilst the Japanese attempt to defend with about 14 divs (give or take) . Using the old silk road route through Kazakhstan (the route they used to supply their version of the flying tigers fighting the Japanese in China before 1941) would be used to pour men and material into the CCCP formations fighting in northern China.
People are surprised to learn that for the first six months after their entry, the US was a net liability to the allied cause. Despite the heroic and effective war being waged in the Pacific, this does not compensate for the netlosses being suffered in the Atlantic, nor does it compensate for the considerable aid being provided under the reverse lend lease arrangements that were occurring allover the world. The US was a sleeping giant, that once awaoken would seal the doom of the axis powers. However it would take some time to achieve that, time to teach the Americans how to fight, time for the Americans to leearn some very bitter realities. If those experiences are removed from the equation, the allies in the short term are better off. What I will concede is that a delayed entry of the US into the war is going to have a negative effect at the end of the war....towards the middle and late 1944m, because it will take the US that much longer to gear up for war, and Germany may have enough time to get her wonder weapons in place.......