I'd say though that the differences between American accents tend to not be as different as depicted, especially with the media and internet which I believe is converging dialects. For example, I live in Canada but pronounce many words the American way due to the influence of media.
Well I live in the Southern US and have relatives from Ohio so I get a good dose of the spectrum. There's some pretty wide variants. For example, I doubt you pronounce "wash" "warsh" and "fire" "far". The thing is we have big regions with these accents and then in between each is considerable bleedover rather than sharp, pronounced areas where these dialects and accents form. Except, of course, where geography has created subdivisions of sorts. But there are a lot of younger people like me with little discernable accent because they are exposed to a lot of them together plus television and other media exposure.