It's unfortunate, but the stereotype of inbred white trash is still alive and strong when most people hear Appalachian drawls. They hear the way we talk and immediately think we're ignorant. It's an openly-mocked culture.
I worked on Wall St for over a decade. I regularly walked into the corner store (Duane Reade) in a high-end suit, $300 Thomas Pink shirt, cuff-links, a tie, and shiny shoes. I also had the mannerisms i was expected to take on having gone to an Ivy League undergrad.
Still on at least 5 or 6 occasions, individuals would walk up to me and ask "oh which aisle has the detergent" as if being of Indian origin automatically made me the store keeper. They saw right through my impeccable outfit, ignored it all, and saw "the Indian store-keeper guy."
Got a link? I'm not questioning you, I'm curious to know more.
A conversation with the Wash U financial aid office made it very clear just how bad the low-income white situation can be. We were working on my financial aid package and trying to figure out some way I could get the loans and grants I needed (I nearly had to quit school) - and as the woman was looking through her options, she jokingly asked if I was hispanic, saying they had a number of full-tuition scholarships and other funding opportunities for black and hispanic students plus a few opportunities for inner city St. Louis residents. Nothing targeting the low-income and rural.
The good news is that they (along with many other schools) later dropped the race requirements for their scholarships. They also offer free tuition for most, if not all, low-income students now. Sadly, those changes were too late to help me avoid $100k in student loans.
Even now, though, I wonder if many rural students would know about those opportunities. When I was applying to colleges, I went through a couple guidance counselors before I found one who didn't try to talk me into going to community college and studying something easier, like cosmetology or secretarial work. It takes an abnormal amount of effort and drive to get beyond that kind of rural upbringing and educational system, but people tend to ignore the fact that white people can also have a lot of systemic disadvantages.
This also hurts immigrants from other countries: they may be well-educated but on first sight they appear to belong to a lower class. It's very unfortunate.
There's also the reverse effect, notably lampooned in the film Love, Actually: if you've a British accent, Americans will assume you're posh.