I don't think that is correct, the Klimov was a Hispano 12Y, just taken down a slightly different development path. The Soviet difficulties in developing the engine further, in spite of significant efforts, are more of a reflection of their difficulties in industrialization and high tech in general, which they did largely overcome during the war. There is a reason why they started out with the French design instead of developing their own inline engine from scratch, as it were. They were going through a very steep learning curve. Their development cycle also reflected the different (lower grade) fuel they used, by necessity.
Read up on the Russian engines again. In 1932-34 the Russians signed deals for license production of the Hispano 12Y, the Gnome-Rhone 14K, the Renault V-12 air cooled, and the Wright R-1820. This was, as you say, to steepen their learning curve. It also gave the Russians access to the improvements made for a number of years after the initial deals were signed which varied in the amount of later improvements passed on. The Russians were not floundering around the tundra in 1935 trying to figure out improvements on their own.
Look at the fuel situation again, in 1932-34 everybody was running on 73 to 87 octane fuel and those years mark the time that 87 octane fuel became a defacto standard until the late 30s. The US lead the way but only to 91 octane. You also didn't even have standard 87 octane fuel in the way that you have "standard" 91 octane and 100 octane fuel by the end of 1940. beginning of 1941.
A lot of people knew better fuel was coming, they didn't know exactly when or what it's actual capabilities were going to be. Russian fuel problems as far as engine development go didn't show up until 1940-42.
Again, was USA on a war-footing when the 12Y development was interrupted (or at least, drastically slowed down)?
I gave one example of the US being on war footing in 1942 to 1943.
How you got 1940 out of that I don't know.
Now we have to define "war footing".
US industry was moving to war footing somewhat faster than many people believe.
The US built 3 times the airframes and engines in 1940 than it did in 1939 and it tripled the production in 1941 over what it had done in 1940 (9 times total) and it roughly tripled things again 1942 (27 times 1939 production) and no it wasn't because of Peral Harbor. Most of the planes built in 1942 were ordered in 1940 or 1941.
So when did the US move to a war footing? For a few hints see Roosevelt's speech of May 16th 1940. See when contracts were signed for brand new engine and airframe factories (like the deal with Packard).
R & D on a lot of French engines was not what it could have been during the 30s, which means trying to play catch up was going to take a few years. The Hispano and G-R engine also had the restriction of trying to incorporate old tooling to keep cost down. And nobody else was trying to up date a 1928 engine with legacy tooling and concepts dating back to 1918. Allison sure wasn't trying to update the Liberty engine.
Ok well, the 14M was used in the successful HS 129 and was selected by the Germans as a replacement for their own Argus As 410. So I don't think it was so bad.
There are a few arguments over that one. But the 14M didn't get sand filters for a while so perhaps it had an excuse.
However we are back to the 14M being a Red Herring on the 14K, 14N, 14R development path.
I don't think postwar development of a radial engine is comparable to pre-war or wartime development, it's basically back burner by 1946.
Depends on which countries.
P & W certainly spent a lot of time and money on piston engines in the late 1940s. Several post war versions of the R-2800, the R-4360, the R-2180 (that one didn't sell well)
Wright spent a lot of time and money on piston engines in the late 1940s like new versions of the R-3350, the R-3350 turbo compound, new versions of the R-1820.
Bristol spent a lot of time and money on new versions of the Hercules and the Centaurus.
They may have been back burner for some military uses but they were key to commercial sales that would keep the companies afloat while military contracts for jets zig-zagged all over the place.
For a few years after WW II ended they were still researching higher performance fuel than 115/145. See Cook Cleland and his Corsairs in the 1948 Thompson Trophy race.
After 1945 they also had a lot better idea of what worked and what didn't and they had much better test instrumentation/test stands/house than they did in 1940.
And the French made just about zero progress in the post war years (money, disrupted factories, general conditions in France ?) or perhaps they over sold the 14R in 1940 and were trying to get a production version up to what they had promised.
I don't think it's fair to make a direct comparison with engines which were intensively developed from the 1930s through 1945 with ones that basically stopped in 1940.
To do so (and to try to rationalize it, no matter how erudite a fashion) is a bit misleading.
Once again, the Hispano dated from 1928 (at best, that was when it was cataloged/announced and not when development started) and it had a 12-18 year run.
The Allison dates from 1930 but had a very protracted (no money) development for most of the 1930s.
The Merlin dates from the early 30s and also had a number of twists and turns before production started in in 1936/37.
The DB 600 and Jumo 211 are both from the early 30s.
The Hispano was simply 8-10 years out of date.
Insisting that this almost antique had much development left is a bit misleading.
So is blaming the poor development history of the Swiss engines solely on the Swiss lack of industry (which seems not to have been true).
Some engines were vary adaptable to upgrading, some were not. Please look at the whole Wright radial line. To keep it simple stick to the R-2600. Once it hit 1600hp that "version" stopped. To get to to 1700hp (and an extra 100rpm) required changing the crankcase from Aluminum to Steel, and basically everything else to go with it. In fact the original factory only built 147 of the new engines before all manufacture of the new engine was transferred to Cincinnati. Old engine stayed in production until just about the end of 1944.
Going to the 1900hp version required another new crankcase and brand new machinery for making the cylinders and cylinder heads. It took 2 years from the 1st R-2600BB test run to the 5th production engine. Granted Wright was trying to manage the R-1820 and R-3350 programs at the same time.
Claiming the French could do what no other in country was able to do either before WW II, during WW II or after WW II seems a bit much.