What are the differences between American and British rock vocals?
ie Beatles and Queen, vs Nickleback (ok, hes canadian, but its north america) and Nirvana
In other words, us rockers think that its cool to scream and all that for some reason, even though it sounds bad and grates on the ears (im from us btw, but i like the british vocal style much better)
Im not comparing nickleback and nirvana, im just pointing out that north american bands like distortion and screaming. If you want an earlier example, try GnR (i love Axl, and he is from the very, very few that make the screaming sound somewhat good. But i still think hed be better without it). Queen started way before gnr, but they were active at the same time. Im sure that someone with better knowledge of early rock music can find even earlier examples of american style vocals. Even Van Halen's vocal style was very different than the clear sound of Queens or the Beatles
Which British rockers sound American when they sing? Certainly not the Rolling Stones.
The fact is that "correct" diction for singing is nearer to a British accent than to an American accent so lots of people hear a British accent in singing as being "with no accent at all." Many American singers, even in the pop/rock genres, modify their diction to be closer to British English because singing with an American accent tends to sound like a "twang." Think country music - that's American diction in singing.
Nearly all Broadway singers have had enough training that they know how to modify their diction but the extent to which they choose to do it depends on the musical and the role. I honestly can't imagine why anyone would choose to sing "My Fair Lady" with American diction, though. I mean, the whole musical is about learning upper crust British diction.