No, it's because America threw those roots off twice in it's history.
America didn't pre-exist before the British people. It is great because it took the best of Britain and started afresh, without any baggage.
Why do you think you speak English and that you hear of Italian-Americans, African-Americans ad infinitum but no British-Americans?
America was not conquered - it was created by and for Britain, until those British people decided, quite rightly, to throw off the old cr@p. It was the British who beat the British. The settlers didn't come from mars.
That is why, to many American's surprise, American Independence is seen as a great part of British history and why after 9/11 it was possible for Buckingham Palace to play the star spangled banner. No other country would have that right, except maybe Canada, Australia or New Zealand. See the link?