Lots of interesting comments here, including Dys', re educational changes.
Who started the middle america stuff anyway? Was that Reagan?
There can be a tendency, as lightwizard alluded to, to put the coasts at the intellectual edges and the flyover states as the womb of middle america, but most of us know better than that. Middle america seems a marketing idea to me, not accounting for any complexity at all.
I do remember being pissed and barely finishing a book by a guy I previously liked, whose name I'm now forgetting (who wrote the popular book about hiking the appalachian trail?). This book was about some time he spent dashing through Iowa and making rude and insulting observations in an apparent funny way.
I think Panz nailed it - curiosity, continuing curiosity, is the key - and that can show up in all classes, all levels of bank accounts or no money at all, all gradations of formal education including almost none (my father in law stopped at fourth grade and had a life long curious mind), all ranges of religion or spirituality or neither. (I get that fundamentalists of any sort can be closed minded, but some can break such a mold.)
Adding, the anti part, re intellectualism, seems to me to be based on resentment, burning resentment.