The German planes could climb to the high altitudes at which it operated and the P-38 was not maneuverable enough to dog fight. In the Pacific where the Japanese aircraft could not operate at that high altitude, the P-38 was successful diving on its opponents at high speed, using that speed to zip away so that it could then regain altitude and do it again and again and again until it scored a kill. The Japanese planes never got the chance to dogfight against it - they were always the hunted and never the hunters.
Yes and no. The P-38 supercharger was designed to provide the same horsepower from sea level to ~28,000 feet. That is because it wasn't believed enemy fighters would operate higher. War has a way of changing things quickly and once high altitude variants of the ME-109 and FW-190 were developed, the supercharger of the P-38 had to be redesigned to permit higher altitude combat.
All of this happened as teething problems with the original superchargers were manifesting themselves.
True only for later "high altitude" versions of German fighters. But that was just part of the normal move-countermove process of wartime development. Initial P-38s maintained sea level power to ~28,000 feet, above that, power rapidly fell off due to the nature of the superghargers, but that was by design. As German fighters climbed higher, improved variants of the P-38 neutralized that.
In the Pacific where the Japanese aircraft could not operate at that high altitude, the P-38 was successful diving on its opponents at high speed, using that speed to zip away so that it could then regain altitude and do it again and again and again until it scored a kill. The Japanese planes never got the chance to dogfight against it - they were always the hunted and never the hunters.
That is one part of it. The other is that the "inferior" American P-36, P-39, P-40 and F4F had killed many of the elite Japanese pilots by the time P-38s began operating in significant quantities.