To understand the deck layout on the United States, you need to look at the never built 1945 New Fleet Carrier. It was designed from May 1945 through to mid-1946 to incorporate the lessons of WW2 (remember Midway was a 1940-42 design that did not enter service until 1945 so the lessons were coming from the Essex class). To improve flight deck efficiency, all the lifts were moved to the side of the ship and there were to be 4, two on each side. And with more and larger aircraft needing launched more often by catapult a third catapult was required, with the only solution being to fit it on a sponson angled to port so that it would avoid an aircraft on the port forward catapult. But this was still an axial deck carrier. It would be several more years before the angled deck invented in Britain would be developed and adopted by both navies.
Aug 1945 also saw the request for development of what became the Douglas AJ Savage able to carry a 12,000lb bomb load and operate from the Midway class (the bomb load seems to have been determined according to Admiral Sallada's later comment "Analysis of bombing results in Germany has revealed that lethal damage to many targets required 12,000lb bombs." Was he thinking about Tallboy? Friedman notes that "It is no longer clear whether the Savage was conceived from the beginning as a nuclear bomber.")
By the end of 1945 Sallada was thinking about a new 100,000lb aircraft with a 2,000 mile combat radius was proposed which would require a new carrier to operate from. Hence the United States requirement.
This big new aircraft drove the design of the carrier, whose evolution saw it change dramatically from the earliest designs to the one finally signed off for construction. This is all set out in Friedman' "US Carriers An Illustrated Design History". It was the size of the aircraft (est 116-125ft wingspan with perhaps the prospect of greater in future) that drove the flush deck design. Initially it was going to be hangarless, carrying only 24 heavy bombers on its flight deck?
In its final form it was designed around an air group of 18 bombers plus 80 x F2H-1 fighters. A heavy AA armament was also required for self protection. And it adopted a flight deck layout derived from the 1945 Fleet Carrier with 3 side lifts plus another in the stern, and 4 catapults, with one angled to both port and starboard, again to allow aircraft to clear similar aircraft on the forward catapults, thereby allowing near simultaneous launch of 4 aircraft. In the final design the after cats were intended for fighters only. But again still with an axial deck.
The United States differed from previous USN practice in that the flight deck was the upper strength deck, which meant design problems dealing with the stresses around catapults, elevators etc. Some more information here
By the way the Forrestal CVA-59 was designed as an axial deck carrier. In Jan 1953 it was proposed that the angled deck be adopted for the FY 55 carrier (CVA-61 Ranger?) but in May that year that was extended to the whole Forrestal class. By that time both Forrestal and Saratoga were under construction.
The successor to the AJ Savage became the Douglas A-3 Skywarrior. The parameters for this aircraft were laid down in Jan 1948 by the DCNO in a letter to BuAer. The highlights were:-
Bomb load - 10,000lb
To operate off the class 6A carrier I.e. United States
Emphasis on speed - Vmax 525 knots + at 40,000ft
2,000+ nautical mile radius of action (1,700 minimum)
Minimum size and weight.
Various weight options were under consideration as well as such radical proposals as no landing gear, refuelling after take off.
Over at Douglas Ed Heinemann and his team were asked to design a 130,000lb aircraft with jettisonable landing gear in Feb 1948. Instead he presented a proposal for an 80,000lb turboprop and a 70,000lb jet. Out of the subsequent competition came the A-3 which first flew on 28 Oct 1952.