Britain was undoubtedly the biggest influence in the rock n roll scene. Britain is where it all got started with the Beatles. The Beatles opened up a new realm of music, music that involved crowds of screaming fans, particularly girls who would fall head over heels for these gentleman playing on stage before them.
Great Britain sent us the British invasion which was one of the high points of rock and roll. However, those in the movement say that they themselves had listened to Elvis Presley and American jazz performers before they got big in music and developed their own style so it was a collaborative effort.
In the 1950s, as American Rock and Roll started to arrive in Britain and the rest of the world, singers like Cliff Richard and the Beatles in the UK, Bobby Solo and Little Tony in Italy, Johnny Holiday in France, Brendan Bowyer in Ireland etc. etc. started to copy the music, fashion and style of American singers, mainly Elvis Presley as he was the biggest. His films also had a huge influence, especially Jailhouse Rock and King Creole. Have a look at this video where Paul McCartney talks about going to his first Elvis movie. Http://www.Youtube.Com/watch?V=mm-6SSwXgfo
The Beatles started out as a cover band. If you go to their museum in Liverpool you can see the set list for their first concerts, it was all covers of Elvis, Little Richard, Jerry Lee etc.
So the answer is definitely no.
Not just Britain and America. Several countries have, and still do, influence rock 'n' roll. There's no doubt Britain had some of the most prominent influence on rock 'n' roll, otherwise we wouldn't be debating this question. But many countries in Europe have influenced rock 'n' roll in different ways, and there are quite a few rock 'n' roll bands from Australia.
Rock 'n' roll is evolving, and a lot of different countries have different music scenes (different countries in Europe have relatively distinctive rock music from what I've heard) And there are probably dozens of countries I haven't named that have probably influenced rock 'n' roll in some way.
The British may have extended and perfected some styles of rock n roll, but they certainly didn't invent or heavily influence the core elements of rock n roll. The Beatles and other influential acts version of rock n roll was extracted from blues and from the American artists who had already taken the style and begun to develop it. Britain is hugely influential, but rock n' roll is essentially American.
No, I think that if you look at the roots of rock and roll, you should take a look at the older performers. Pre-Elvis in America there was a widespread movement of African Americans who were doing rock and roll before everyone else. Yes, the UK gave us The Beatles, The Who, and The Rolling Stones but America has always been the pinnacle of music.