Hehe, I'm just beginning the learn the difference between the Aussie and NZ accents, but they're very very similar.
America certainly has an accent. As far as I acn tell, there is the one normal accent (that encompasses Canada) and the other accent, which the Southern one. I personally really don't like the accent, I think it sounds terrible and sometimes can't stand hearing it
Especially when it's very strong. I think this is because I'm not really exposed to it at all; many people I know say they don't notice an accent on programs like The Simpsons at all.
Adversely, there seems to be a difference accent for every fifty miles squared in Britain :s