To tease apart above for non-US readers, to the best of my understanding.

The US government funds most of the resident slots through which the path to become a doctor runs.

The AMA generally (but not always) lobbies against increasing slots too much, reasoning it would decrease the premium doctors (its members) could charge.

As a result, most of the time the US has too low of a supply of doctors, especially in general, highly-demanded areas (family medicine, internal medicine, psychiatry).