I think you're seeing a political aspect to the movie which I'm not convinced by. The staple of all comedy - even something as genial and inoffensive as My Big Fat Greek Wedding - is exaggeration and caricature, and yeah, the characters frequently do end up looking "repulsive and foolish". But to assume that this necessarily means Payne is making a point about the idiocy of all middle-Americans doesn't make much sense. It's like saying Fawlty Towers is John Cleese's attack on residents of Torquay, or Sideshow Bob on The Simpsons is a vessel for the writers' distrust of well-educated childrens' entertainers. Just because the movie is set in a particular place doesn't mean it is intended to be representative of that place, just as David Lynch had to point out to critics of Blue Velvet that just because Dorothy was a woman doesn't mean she was an avatar of every woman.