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.
Do you pronounce pin and pen the same way? I do, but apparently most northerners don't, so I don't know where I got that from.
I pronounce them slightly differently. Hard to say where you got that, I'm not sure it's a regional thing or just a speaking quirk some people pick up.