I've finally had time to look over the whole thread. And it seems to me, the Brit-Side has mentioned only musicians in the vein of rock or pop. While these banRAB were very good (Beatles, Who, Oasis... etc) Rock and Pop aren't the only two music genres out there. In my personal opinion, there are about 4 or 5 genres that the Brits can't even hold a candle to.
Rap.
Hip-Hop.
Country. (Southern Rock, Bluegrass, Honky Tonk included)
Jazz.
Funk.
Heavy Metal. (the Brits could put up a fight here...)
Emo and all of it's subgenres.
Ska.
Just to name a few... Americans have dominated these categories since their inception. Now, I don't know everything about the British music scene, so if you think I'm missing a huge band in one of these categories from Britain - please let me know. So while you may do rock, and it's many sub genres well... you are simply stuck to that corner of Musicdom. Looking into the popular/influential/pioneers of these genres, you might - MAYBE - be able to pick out one British group (save for heavy metal) - but even then, the one or two groups wouldn't be able to match up to the absolute american rule over those genres... Hell... Country IS American. Also, the Brits would have nothing to build on if the Americans didn't create it to begin with.
In conclusion: While the Brits do the things they do well (not necessarily better) - There are certain genres that they have yet to even explore - let alone claim to be better than an American counterpart.
Which would you rather have?
One robot that does 2 things very, very well.
Another robot that does 7 things very, very well, including the 2 things the first robot did. Not only does it do the other robots specialities, but just as well if not better than the first robot.
Get it? Now, those nurabers are purely random so don't ask me what the 2 things are and be stupid. So I think that fact alone raises America here. The Brits do a few things very well, but don't even begin to sprawl out and hold sway over the amount of genres that the Americans do.