Hey, love the idea. I played a game as the US, and I had a couple of notes:
1) Is the US Supposed to be on moderate Mobilization for the whole inter-war period? I enter the Great Depression with like 5000 manpower, so I was just curious. On a Similar note, the Immigration act event gives you flat Manpower outside of mobilization, and that adds up to over 1000 once WWII starts, which is probably not intended. Ideally, not passing the act should increase the manpower values of a couple of American provinces, though I'm not sure if that's doable There should probably also be a hefty Dissent penalty for not passing it.
2) Are the Great Depression events supposed to fire as normal? Because the net result is that the US loses like 200 IC but then gains 40% free IC Efficiency, since the way its modeled is different in the AAR mod versus the Day of Decision stuff. I imagine Germany's does as well. It might be better to coordinate these events--maybe make some of the Great Depression events sap IC Efficiency instead of raw IC?
3) The US is still on the -50% Wartime IC modified from WWI. You might want to consider adding +10% to that on some of the US militarizing events like the Arsenal of Democracy and such.
4) The US's air force limitations seem to be bugged. It says I can only build 1 of each type, but it effectively lets me build none at all.
5) A better way to handicap Germany, Japan, and the USSR's IC-spamming would be to give them a +300% IC Build time event like what the US gets. Maybe get rid of it once the 5-year-plans start coming into effect or something, and when the New Deal starts.
6) You might want to fix the "End of the Warlord Era" events for Nationalist China, as they check for whether or not Communist China exists, and as a Result Nationalist China can usually unite the entire country before the Communists even show up. Though honestly, this actually gives Nationalist China something like a fighting chance against Japan, since Nationalist China doesn't seem to build any IC and winds up fantastically under-powered once Japan starts to invade.
Thanks!