If the UK and USSR are capably handling Germany and Italy by themselves in your games, you as the US should be going mostly Pacific.
You can build fleet (including loaded transports) and stage if off Queensland for the moment when the US magically enters the Allied side and all of a sudden has a naval base to spring from. So, while Japan might grab the Dutch East Indies and hold them on its turn, the US right behind it turns those islands into American territory (and American IPCs). If Japan deployed fleet to cover individual transports that took islands, then the US has an opportunity to destroy the Japanese fleet in detail rather than in one grand battle. If not, any islands you don’t recapture still lose their uncovered transports and the forces there are stranded.
It will take Japan at least two turns to get new loaded transports in a position to attack India or recapture DEI (more if they did not build them the same turn the DoW was issued), and by that time the US fleet can have turned north and presented a challenge to the IJN. So, while the sudden Japanese expansion might be scary, it will peter out as long as you are in position to counterattack it. In fact, it is probably only working against you because you are hanging back with the US and not pressuring Japan.
Consider that once the US goes to war, its income is higher than Japan and both nations share the same logistical concerns – new naval units are built the same distance from where they are needed. If you 1-1 swap ships with Japan, you are winning the economic war in the Pacific because Japan cannot afford to rebuild navy to challenge the US and also win the game at the same time.
Also consider in the Pacific that it does not matter if India falls as long as the Allies hold New South Wales, Hawaii, and Western US. You could turn Hawaii into a mega fortress with a fleet around it that can sail to the relief of Australia with an accompanying land force, and during the same turn build replacements in Western US for whatever you send to Australia.
Marsh