I read somewhere that theres a tiny island near Austraila or somewhere with about a 80% obiesity rate. *shrug* Can't remember the name though, so that kinda makes it irrelevant.
IMO yes, America is a fat nation. I saw a lot of fat people when I visited. (Yes I know I hardly saw an accurate slice of American culture/representation of people blahblahblah)
England is fat too, loads of fat kids....I find it scary.