The optimal strategy vs AI si to build up Guam and another close island to level 10 ports, then prepare for war in Q4 1941. As soon as war breaks out you move about 20-30 divisions to Tokyo, escorted by 3-4BBs and 3-4 CVs (+ screens) and do a rapid landing to sieze it. Then you ignore the pacific islands. You'll probably lose some ships, maybe even big ones, but it's game over once you sieze Tokyo's supplies and fan out to take the Islands.
Super cheesy, but it works erry time - at least no normal
I try to avoid the super cheesy. Part of that approach includes bottling up the Japanese fleet in some port and just hammering it to death. It feels too easy to me.