The British got the first batch, and needed planes, so they didn't wait for the superchargers. Probably had a lot to do with it. Then there was a problem with the flaps that need modifications.
That's not to mention bailing out. The pilot had to crawl out on a wing, over an engine, before dropping, to avoid being hit by stabilizer.
I seem to recall that the British P-38s didn't have counterrotating props either.
Then there was a problem with the flaps that need modifications.
If I remember correctly, that was a compressibility issue which was a common, yet poorly understood problem affecting most advanced fighters of WWII. The P-38 was just one of the first planes to experience compressibility and therefore got a unjustly bad reputation before other fighters like the P47 and P-51 came into service.
That's not to mention bailing out. The pilot had to crawl out on a wing, over an engine, before dropping, to avoid being hit by stabilizer.
Clearing the tail members was a concern when bailing out of any fighter.
In the case of the P-38, I believe the pilot only had to get out of the cockpit and sort of slide down off the wing and he would usually pass beneath the horizontal stabilizer.