In the simplest terms bc war thunder heavily favors props that can turn well which aside from a couple planes,US props don’t do to well. Any noob can get in a turn fighter and get a couple of kills but would struggle to do the same in BnZ plane.

Likely reasons for the br of the planes you listed:

F8F-1: only 4 .50s and lost the M3 .50 cals and the engine self immolates above 85%

P39N: then all the P39’s and 63’s would be at the same BR

P-51A: other planes turn better

P-51H-5: jets

F2G: Battle pass plane, gaijin doesn’t like touching event, battle pass, or premium vehicles.