How American shipbuilding could recover from a lost 1941 fleet

If the entire US Navy disappeared in 1941, how long would rebuilding a fleet capable of defeating Japan take?

New American ships would begin arriving around 1943, but Britain would probably have to complete additional warships to bridge the first two years.

In this counterfactual, the American construction program already on order would begin restoring naval strength around 1943. The first replacement ships would therefore draw on work begun before the imagined destruction of the fleet. The intervening two years would leave the Allies with serious gaps in their deployments. Britain would probably have to finish additional capital ships and other warships to cover some of those immediate commitments.