We have friends who are from London. They explained to me the difference between Michael Caine's accent and their's. They tell me that they grew up in different neighborhoods and that their accents are very different. However, I can't tell any difference. I'm sure their is one, but to my ignorant American ear, I can't detect it.

It's really the same with Americans. Even within NY, we sound radically different, forget about comparing someone from NY to someone from Kentucky to someone from Texas. It's all different.