FDR was desperately trying to find a way into the European and Pacific wars well before Pearl Harbour. By then, for example, he'd taken over the protection of Atlantic convoys for half of their journey to Britain. He'd also introduced peacetime conscription for the first time in US history, and started a huge military build up - again a first in peacetime, since until then the US had generally maintained rather anemic land forces except during war. The Republicans were hardline isolationists, and with a minority of the Dems made a declaration of war politically impossible.

I'm also not sure how the chaotic mess that was China in the thirties posed any sort of competition. Russia for its part was an ally of Germany's until it got attacked.