It never happened my FRiend, for Kelly Johnson insisted that the RR Merlin be a part of the P-38 and it was denied politically for it was promoted that an American engine be used instead of the venerable Merlin.
The P-38 however toted a (new for the time) turbo charger but it was found to be plagued with issues that made the P-38 a more formidable fighter at low altitude, thus it's claim to fame came about in the Pacific and not in Europe.
Was'nt the engine changed late in the game that gave it an edge in europe??