I'm especially interested in hearing from UK English speakers on this one. The last few times I was in the UK, I was often taken for a Canadian, which I blamed on my Minnesota accent, which seems to be growing thicker all the time. However, that only happened when I was travelling alone - the few times I was with my friend or my sister, both of whom are much louder and have what I would consider distinctly American accents, no one ever asked if we were Canadian, American was always assumed.
I brought this subject up recently with some folks, and they seemed to think that being asked if I was Canadian was because Canadians tended to be upset when assumed to be American, but not the other way around. I'm not so sure about that, though - even going on road trips in Eastern Canada and the US I was either assumed to be from Western Canada (by the gals behind be at a Blue Jays game) or just Canada period (in Boston and Virginia). Recently even someone from my hometown who I met at a friend's house asked me if I was Canadian! I wonder if my accent hasn't started to pick up some more Canadian traits after moving around so often? Does it matter? Sometimes I can't even convince myself I'm not from Canada.
tl;dr version: I'm moving to London next week. Do you think hearing me will have people assume that I'm Canadian, or do people not even care? Also, Canadians: are you really offended when people think you're American?