I think some HOI fans are ignoring that HOI is also trying to simulate the economic situation. There's lots of talk of huge industrial capacity, but in 1936 the USA is still in a recession, about to encounter another downturn. There is a lot of capacity, but not as much as the hindsight of 1945 implies, and a substantial section of the existing capacity isn't being used because of the depression; millions of unemployed and empty factories. Also only a tiny proportion of the production is for war material because there's only small armed forces.
The Challenge to someone playing the US is to build the massive war capacity before its attacked. I think its a bigger challenge than many think and they're underestimating the skill of
Roosevelt in doing as well as he did. I found a quote about this "In the years before the war, he had been very conscious of the deficiency in French air power and had attempted to assist her air rearmament" Indeed he knew that by encouraging large French (and British) aircaft orders it would be giving the US air industry a massive boost. So we get the situation that the US administration is still accepting big aircaft orders from France even in 1940 as the collapse began. If you look at US air production figure you'll see big increases in 39/40 mainly the result of this.
So I think its only natural for the US A.I to leave it as late as possible before entering the war, whilst it finds all that capacity. Roosevelt himselft unlike many had very little confidence in the French armies ability to stop the Germans even in 1939. So I'd expect the AI to sit out the fall of France and much else.
As a matter of interest does anyone know how the game replicates Britain having to sell all its foreign currency and assets to get US war material before Lend-Lease came in ?
I think the clues on how to defeat the USA are in the History of the time. I don't know the game mechanics, but I'd guess trying to slow down US rearmament by encouraging internal US decent are possible ways to cripple this potential giant. If the US becomes a battleground for diplomatic and influencing actions from all sorts of powers, we could see some very interesting results. Though I'm not advocating anyone tries to invade it in 1936, as that would be counter productive; the US doesn't really have an army, but you don't have any real means to sustain an invasion force across oceons control by the British and US Navies.