That's very interesting, I've listened to Bon Jovi and Madonna and some other singers trying to make some observations. Bon Jovi really seemed typically American to me, so does Mariah Carey, but still I'm not sure that if I heard them without knowing who they are I would be sure that they are American. Madonna is not so typical, neither is Barbra Streisand. I think it also depends on the certain song and the style. For example Whitney Houston didn't seem typically American in the song 'Love will save the day', but seems typically American in some other songs. It's interesting that when I heard Celine Dion for the first time (the song 'Think twice') I thought she was American and I was very surprised when I heard that she was French-Canadian and learned English only when she was an adult. I also couldn't guess that my favorite group The Carpenters was American and didn't know it until someone told me. Well, maybe that's only my lack of experience.