Among other things the Brits didn't like it because the version they received early in the war (prior to Pearl Harbor) didn't have the turbo chargers installed because the Army Air Corps considered the technology secret and not allowable for export. Also the 8th Air Force was controlled by the "Bomber Mafia" at the time P-38s were available and they didn't want fighter escorts for the bombers. They actively quashed the whole idea of escorting bombers on missions to Germany. In the Pacific, the P-38s range was greatly appreciated so most P-38 production went to the Pacific.
As a side note, the F-5 unarmed photo-recon variant was highly successful in all theaters of the war.
Greg’s Airplanes and Automobiles is a great site for highly technical non-AI-slop WWII aircraft vids. Highly recommended. Greg is scathing in his critiques of the Bomber Mafia. We could have been escorting properly early in the war.
His main channel:
https://www.youtube.com/@GregsAirplanesandAutomobiles
P-38 playlist. First vid there is titled “The P 38 Lighting and the Bomber Mafia’s Failure In World War Two”
https://www.youtube.com/playlist?list=PLD2EcpzcvT-tbzZrbEuetBOalWtEiILpF
Agreed. Back then products were deemed "good enough" and then shipped out for customer field testing. Had the British order contained P-38s with counterrotating engines and the superchargers, teething errors with the combination of British aviation fuel and high altitude operations could have been identified in the 1940/41 timeframe and corrected in updated variants by the 1942/43 timeframe.
Also the 8th Air Force was controlled by the "Bomber Mafia" at the time P-38s were available and they didn't want fighter escorts for the bombers. They actively quashed the whole idea of escorting bombers on missions to Germany.
That may also have influenced the pilot controls which were too complex for the average pilot... at least when flying with British aviation gas at high altitude in winter under emergency combat conditions.