Because of limitations with propellers, performance wouldn't be much better than late 40's planes like the F8F, Spiteful, AD-1 Skyraider and similar aircraft.
I agree though, if the USAF built one, they'd make an ugly POS with crappy performance that costs 10 times whatever anyone else is using, then be afraid to use it in combat because it might get shot down.
J_A_B