Jane-DoH:
Why was the USAAC/USAAF so averse at first to using turbochargers? They work better than superchargers, and the technology existed since at least 1918.
The Army Air Corps was NOT averse to turbos. Republic, Lockheed, and Curtiss all built prototypes using Army-specified turbos, and the P-47 and P-38 (both with innovative layouts) won production contracts. Likewise the B-17 and B-24.
Had NAA proposed the Mustang first to the US Army, it likely would have had a turbo just to win the contract; but the British were first to the table, and (at that time) they had little use for the turbo. The British even bought "P-38s" (Lockheed 322) hobbled by lack of turbosupercharging.
In fact, the Army flight-tested a LaPere bipe with a GE-turbosupercharged Liberty engine in 1919, setting a new altitude record in the process. In 1936 they had Lockheed build the XC-35 research aircraft with turbos and a pressurized fuselage - the first aircraft to used the monocoque skin as a pressure vessel.
New question: What was the first aircraft to use supercritical airfoil AND turbosupercharged engine(s)?