The USN was the largest navy in the world (technically tied for it with the RN) for the entirety of the Washington Naval Treaty system. When the naval arms limi

The USN was the largest navy in the world (technically tied for it with the RN) for the entirety of the Washington Naval Treaty system. When the naval arms limitation treaties broke down, circa 1936, their spending ramped up at about the same pace as the other two nations that matter (IJN and RN), e.g. the first battleship commissioned by any of those 3 navies after the breakdown was HMS KGV (Oct 1, 1940), the second was HMS PoW (Jan 19, 41) but the third was USS North Carolina (April 41). They had actually spent an awful lot on naval technology during the 1930's- e.g. they had the best engineering plants in the world thanks to their small tube high pressure boilers that enabled unitized machinery. As for combat experience, of those three navies, the only one with serious battle experience was the RN- and Jutland was so unlike the aero-naval war that actually occurred 1939-1945 that it is actively misleading (e.g. for Jutland the RN apparently forgot to signal to HMS Campania, the only seaplane carrier in the Grand Fleet, to make steam, so she was left behind. Such a mistake would have been unthinkable during WW2). What might be confusing you is that while the US spent a large amount of money on its navy, and quite a bit on its air force (at the time technically still a part of the US Army as the US Army Air Corps), it spent very very little on its ground forces- in 1937 the US Army ground forces were smaller than that Yugoslavia! That was the branch that came from nothing, with very little experience, and grew exceptionally fast. It did indeed lead to problems during the war, as a whole lot of people got a whole lot of promotions very fast- e.g. General Mark Clark made O5 July 1, 1940, and was made O10 March 10, 1945. The 1937 UK army was larger than the 1937 US Army, and the US Army at its peak was about 3 and a half times larger than the UK Army at its peak, so this rapid expansion is much more notable in the US Army than in the UK. If you look at Army Group commanders during the war, all of the British ones except Leese had at least 1 star on Sep 1 1939; all of the Americans who would go on to command Army Groups were Majors/Lt. Col's except for Devers who was a full Colonel.