I dunno, they would rebuild their carriers.
1. This reduces back to the question of whether disarmament should be a justification for war. We may just have a fundamental disagreement on this issue; however, I think you are opposed, since you are opposed to going to war with Iran to keep them from getting nuclear weapons.
2. The Japanese did not build a single aircraft carrier after 1941 (and each of these ships took two to three years to construct).
3. With what resources was Japan going to build an entire fleet of aircraft carriers? Such an endeavor, at that time, would have meant a reconquest of the islands they had already lost at that point; with their commitment in China, this would have been nearly impossible.
4. Had we packed up and went home in 1942, they most likely would not have had the navy to project power across the Pacific until at least 1945; at that point, they would have been fighting off the Russians.
5. I believe that the Russians, post 1945 (at least post 1950), had submarine and surface-naval fleets that could project power across the Pacific.
We would have been in no worse danger facing a rebuilt Japanese Fleet in 1945-46 than we were in facing Russian fleets from 1946 onward.