Considering the bitter fight between the US Army Air Corps and Navy over airpower and the tacit fiefdoms carved out, I suspect the best bet for a "super carrier" would be the desire to put medium bombers at sea. The USN focused on surging its aircraft so the carrier grew to a size that could launch more aircraft faster, part of this led down the path to smaller carriers so each could launch simultaneously, thus the smaller Ranger (CV-4), but we saw that stall and morph into the Escort carrier classes. The theory needs to shape up faster that bigger was better for fleet operations. That might get us at least design work. My understanding was that the Army got the Navy to be forbidden long range land based planes, thus the Catalina, but I read that the B-17 was supposed to be the biggest Army aircraft too. Had that further delayed anything like the B-29 or worse the slightly better B-24, then one might see a real need to build a "Bomber Carrier." Until we take Saipan and Tinian, the USA has no real means to conduct bombing over Japan, Doolittle's raid becomes the template rather than the footnote. So one gets Super Carriers in a world where the B-29 is too late or not at all? The USN surging PBJ-1H (Carrier B-25s) to strike Japan? Might get that big fleet action sooner for the Battleship fans.