I'll have to read up on Lindburgh - you're probably right about that. IIRC the P38 had an Allison engine to begin with, I don't know if it was a NA or boosted engine; but it was underpowered for the plane. Putting the Merlin, and later the Griffon (the tank engine variant was the Meteor, and was unboosted as far as I know - tanks never really got my juices flowing the same way as WW2 aircraft), turned it, as you say, into the legend that it became.
Hmm, I have a few Jag V12s lying about the shed, it'd be interesting to stick a 2-stage supercharger on one, just to see what it could do...