Close your eyes and imagine this:

Hank Williams finally makes it to The Grand Old Opry. The steel guitar comes in on the first few bars of "Your Cheating Heart" and Hank is about to sing. And then, blow me, Hank starts singing in a Brummie accent!

A ridiculous idea? Perhaps, but not essentially different from what so many British singers do with cod-American accents, even when they're singing their own songs to other British people!