British tone began with the cranked Les Paul through a Marshall...the BLUES/ROCK tone of Eric Clapton in the Bluesbreakers and Cream. That, for me, is where it really started. I know the Beatles, Stones, Yardbirds and the Who and all that came earlier, but for me, Clapton was the man who turned his Marshall up to 10 and overdrove the bejeezuz out of it with a Les Paul playing blues. Even Hendrix wanted to meet Clapton when he first came to England.
American blues players got a cleaner tone and for me, we're talking the tones of Mike Bloomfield and BB King...and Freddie King, Albert King and some others.
So, IMO, Clapton's British Blues created the modern rock tone inherited by Van Halen and others and it was Eric Clapton playing the licks of his heroes through a cranked and overdiven Marshall.
And the American tone is tone of Eric's heroes playing through Fender amps and not playing as distorted as Eric was.
Lew