If the Jap fleet is at Singapore, what stops the US from taking Truk, which threatans all VC’s except Calcutta and San Francisco? What stops the US from landing in Korea? You need quite a few planes in japan to stop the capture of Korea, and those planes are needed in the CBI theater.
x4 fighters and x4 dive bombers.
At least by US2, and maybe even on US3, depending on where the US fleet is based out of.