Now lots of British pop/rock singers sing in - a sort of - American accent.
I say " a sort of" because I wonder if Americans consider that such British artists as have an American accents?
One problem with that is that once a listener knows where a singer comes from, I'm convinced that often the listener thinks they hear a local accent.
I bet the that first time Americans heard, for example, Adele and Amy Winehouse ( without knowing that they were English) they just assumed that they were American.