While it’s not at war, the US may not move units into territories belonging to other powers, including the Dutch territories. After it’s at war, it may occupy Dutch territories (move units there), but it may not take control of them unless it’s recapturing them from Japan.
If you destroy 12 IPCs as Japan the US is down to 38 or so. If Japan keeps up with the US Navy builds it seems like that would keep the Japanese on a pretty even playing field with the US.
I use the US fleet to build up in Hawaii (and position two DD’s in front of HAW seazone to prevent an all out attack) or Alaska. Then Japan needs the larger part of its fleet to defend Carolines and other islands. By this time ANZAC has build enough subs to disrupt all southern islands.