Have you forgotten the Thunderbolt? The P-47 was on-par with the Corsair performance-wise throughout it's career. Both used the same basic engine. (R2800) The corsair's was two-stage, two-speed supercharged, while the Thunderbolt's supercharger was fed by a General Electric turbocharger housed in the aft fuselage along with the intercooler. When they finally put internal wing tanks in the P-47,(P-47N) it's range was AT LEAST as long as the P-51's. The P-47's high-altitude performance and dogfighting capability was second-to-none.

As far as the MiG15's engine is concerned, it was a dead-nuts copy of the RR Nene engine. Desperate for post-war sales, the British Govt. approved the sale of a number of Nenes to the USSR. Upon hearing the news, Stalin replied "What fool sells his own secrets?" Indeed. The Russians quickly put them into production. The first Home-grown Russian jet engines didn't appear until the mid-50's.

This is an area where the Brits never seem to get the credit they deserve. The first "American" jets were powered by license-built copies of British designs. The Brits not only invented the steam catapult, they also originated the angled-deck concept as well as the fresnell lens (meatball) landing-light system. All are still in use today. While we're at it, they also invented the afterburner, though they called it "reheat". A lot of this was given to the U.S. after the war to help satisfy their massive debt to us incurred during the war. Personally, I think they kinda got screwed.