Tough question without maybe being more specific. Is that for instance counting grunge? where you have bands like Nirvana and Soundgarden? Or how about glam rock? Such as Def leopard and Poison? Actually maybe those should count against us. Ha.
MickS' list for Britain is pretty darn good, but I think for America you have to throw in some of the Woodstock era groups: Janis Joplin, Hendrix, Santana, Grateful Dead, Creedence, Sly and the Family Stone, The Doors, etc. But then again, from that group, Britain gets The Who and Joe Cocker. Hmm? That's a tough one. If you could only put up 5 bands I think Britain's got it. Stones, Beatles, Zeppelin, Sabbath, and the Who. Probably the Grateful dead and The Doors belong in that same category, but I don't know if I could come up with 3 other American groups that do.