Um, there was the T-6 Texan. Also, they had 'obsolete fighters as trainers. Also, the US had Florida and Lake Michigan. Florida was year round flying. Lake Michigan afforded carrier landing. A problem as notes in the P-38 article, was that many pilots were switched from one type of fighter to another, in their theater. Most of the had a few hours on the ground and had to learn on their first mission.

If you have seen 'Tora, Tora, Tora', remember the scene with the woman flying the biplane. Then it is surrounded by Zeros? I always though it was a woman being trained and OGM. No, she was actually a phenomenal pilot. One of the better woman pilots of her day. She if ferry planes as a WAC. I think she died ferrying a plane.