Given the completely different strategic situation ITTL, I don't see Japan making any moves against French Indochina or the USA. The fall of France was a major game changer in world politics.
Japan never attacked Indochina IOTL - it was unopposed. The Vichy authorities simply accepted Japan moving troops there because they couldn't do anything about it. ITL, any attempt by Japan to move into Indochina means war with Paris. Which means Japan is at war with both France, Britain, Australi, and Canada (and likely the Netherlands as well), who aren't at war anymore with Germany.
Japan doesn't even have the opportunity to attack the USA because they are engaged in a major war against the Allies in the South China Sea. At best Japan has some naval victories and lands some troops, but by late 1941 reinforcements from Europe begin to overwhelm the Japanese. Allied operations are likely limited to supporting China and reopening the port of Canton. Besides naval action and cleaning up any landings on their colonies, the Allies probably keep any independent actions to landing on Taiwan. Otherwise, they help China kill as many Japanese as possible while Chiang Kai Shek slowly pushed Japan out of southern China and then pushes into central China towards Nanking. If Japan still refuses to make peace, then eventually a push into the north China plain is made, and eventually into Manchuria.
The USA, who has a President that is not FDR, and who knows could even be Taft, is involved merely as someone offerring to mediate a peace.