of American, NOT English, genres such as pop and rock.

WAV - how many times? These genres aren't American in any sort of sense other than one that might be vaguely geographical, given the African, British & European cultural diasporas by which they came about & continue to come about. To some extent one might say Jazz is American, albeit African-American, but ignore the universality of such a music, or yet the universality of its relevance, at your peril. Like folk, these genres are but part of an ongoing process of musical & cultural coalescence of such vast complexity that it might not make much sense to you given your somewhat narrow remit on such things, but it can be just as traditional & English if not more so as any of the folk music you're always banging on about.

By your definition Joy Division played American music, which just isn't the case. I urge a rethink on this, WAV - seriously.