A comparison that assumes U.S. Navy anti-aircraft strength was already the wartime standard in 1939 uses the wrong baseline. British carriers and other large ships began the war with some of the heaviest anti-aircraft defenses then fitted afloat. The United States observed the early campaigns, increased its batteries, and then expanded them dramatically after entering combat. Every navy's fit evolved according to industrial capacity and operational experience. A fair comparison has to use the same date rather than project late-war American armament backward.
Notable Point · 2:23:13-2:23:51
Royal Navy carrier anti-aircraft defenses in 1939
Before wartime expansion, British carriers already carried unusually heavy anti-aircraft batteries; the later American advantage grew from watching and then entering the war.