I would suggest a continued focus upon the domestic policies of the USA. You briefly went into it but the Domestic Policies will in fact have a much larger impact upon America than WWII could possibly have.
I also doubt that the Japanese will attack the US, Unless you Plan on having America embargo Japan's Oil Reserves like OTL...
I also doubt that the Japanese will attack the US, Unless you Plan on having America embargo Japan's Oil Reserves like OTL...