RF wrote:
Two key points - the US submarine campaign off the coast of Japan and its conquests would still have happened, destroying most of Japan's merchant shipping and a large part of its surface fleet.
Secondly the US Navy isn't just aircraft carriers. Carriers were less important in the Atlantic, where the British were using convoy escort carriers. US battleships would still be available for Torch even if Roosevelt sent all US carriers into the Pacific.
The USN submarine offence is often looked at as a foot note to the war in the Pacific, but the truth is that the Japanese Empire was sunk by USN (and some RN and Dutch ) submarines. The USN succeeded were the KM failed: to cut off and blockade, starve, and destroy the ability to make war, an Island nation by submarines. And this was all done with a very faulty torpedo for two years of the three years it took to do it. It was just as important, if not more so, as the carrier operations to victory in the Pacific.
Midway Island was a key base for US submarines though. Subs on the way out from Pearl stopped to top off fuel tanks at Midway and without that they would not have bean able to stay on station within the Japanese Empire's shipping lanes (7 more days sailing to the west on the surface to get there) for long. Midway also served as the most important forward base. Subs returning from patrol would often just go to Midway instead of all the way to Pearl to re-torpedo and to refuel. Taking Midway would have been a major blow against USN sub operations.
The USN would have certainly transferred all their remaining carrier assets to the Pacific without question, and transferred the remaining old battleships to the Atlantic. New battleships like Washington would have been sent directly to the Pacific with the remaining US carriers.