While Japan’s military grew powerful in the 1920-30s, in America:
- Lack of government funding made peacetime maintenance of the U.S. Army difficult.
- The Naval War College created the carrier doctrine, before a single aircraft carrier was operational.
- The Army, and its Air Corps, emphasized professional military education, with little focus on innovation or the development of new capabilities.
- Theories of air war were largely unproven.
Here’s an interesting analysis from the Institute of Defense.