My friend's coworkers, who we hung out with a couple of evenings here in Seattle, are very cool, but not very bright. I kept having to explain to them that I don't have an accent; they have an accent. I hadn't realized Americans were so slow.
Their Wisconsin accents were vaguely reminiscent of Fargo, but when they tried to imitate my accent, it just heightened the Fargo echoes even more. How strange that we each thought the other sounded like Marge Gunderson, and denied that we ourselves did. (Sorry, I'm aware the pronouns and syntax of that sentence are a little suspect.)
I've always thought my western Canadian accent was indistinguishable from a midwest American accent. When I travel or when I lived abroad, I'm usually pegged as American, even by Americans. I've often disappointed people and had to explain that the oot and aboot accent is really more of an eastern Canadian thing. But when I interviewed the Bones creator, I asked him "whereabouts" in Canada he was from. (I would've sworn I never use that word, since "where" works just as well, but then I would've sworn I don't say "about" in any peculiar way, either.) He had a good laugh because he had no idea where I was from and thought I was trying to be funny and imitate the Canadian accent. So, so much for that illusion.
That's the thing about accents - it's all about context. I don't have one ... until I'm surrounded by silly Americans.