When I was a kid it was the british stuff that wowed me. Zeppelin, Floyd, hard to argue with the magnitude of those artists.
But over the long haul, I have a huge preference for American music. Tom Petty, The Doors, Hendrix, these are artists who started out lower on the ladder but over the years I've gotten much more from them than from anybody. And in the strictest sense of "America," Neil Young is worth a million Englands and a million USAs combined for me. Today almost all my favorite acts are from America, both rock & otherwise.