While the flame breather is right that the USN is still playing catch up tactically with the RN, and the building program of ground units and naval units has not hit stride yet, ITTL the Japanese still have to look east to the USN as well as west to the RN. The war was all about resources especially oil, so they have to concentrate on seizing the DEI, Borneo, Malaya and they have to finish off the PI..or at least marginalize any remaining US forces, to make sure the sea lanes to Japan are "open" - if they don't do this everything else is useless.
With the IJN markedly reduced in numbers across the board in ships and key personnel, and the USA with 4-6 carriers in the Pacific (even if a bit green and pilots flying some less than great machines) if they face the RN in SEA the US can kick them in the butt almost at will. Raids on their defensive chain of islands will rapidly reduce them to uselessness because every ounce of fuel used defending against a raid, every airplane shot down, every bullet used etc has to be replaced and the Japanese simply can't do that even with US subs still firing pretty worthless torps (although they do work occasionally). The US (hopefully) will start doing Marine raider attacks (like Makin OTL) very soon using some big subs and/or destroyers converted to fast transports....good politics, good training for the US Marines, and a real pain for the Japanese.
Basically the Japanese are now trying to play whack-a-mole with lots of moles coming from all direction, and a hammer that is getting smaller & smaller.