The Quintessential Alabama film: To Kill a Mockingbird
If being Southern before the Civil War is a bad thing and holding onto that Southerness after the Civil War is considered a very bad thing, then Alabama (along with Mississippi) is widely considered one of the two worst states in the nation. Whereas Mississippi has other points of pride that don't specifically bring up its racist history (the blues, aquaculture, the Mississippi Delta, some of the South's more ornate plantations), there's not as much for Alabama to do except own up to being the epitome of the Deep South which would explain the nickname Heart of Dixie. After all, Alabama today is a center of industry and manufacturing which is something present-day Alabama has in common with Alabama in antebellum days.
Candidates for the quintessential Alabama film ranges from dark films like Color Purple while a film like Tuskegee (or what I imagine Red Tails would be like) tries to simply portray heroism without its contrast. Talladega Nights and My Cousin Vinny also come to mind as films with a specific location but I associate NASCAR as being more of a Carolinas thing and My Cousin Vinny lacks a strong regional flavor. I first assumed it was in the Midwest or Not-So-Deep South before looking it up.
The quintessential Alabaman film, therefore, should be a film that negotiates Alabama's racist past with its progress. It should be a film that's unapologetic about the attitudes of its people back in the day. To Kill a Mockingbird has the quintessential hero in a fight for justice that results in his client not being exonerated. It's a bittersweet film in which the main protagonist (the book's narrator) is a young girl who learns that right and wrong are complicated where they live.
It's a good portrait of small-town Alabaman life as told first-hand by an Alabaman. Although it's primarily known as a book, the film version is iconic enough to appear in the iconic AFI list: 100 Years...100 Movies.
The Quintessential Mississippi film: O Brother Where Art Thou
Mississippi, like Alabama, is known for being the extreme Deep South so we could go for a film that uses the state as a hotbed for hatred such as "Mississippi Burning" or "Ghosts of Mississippi" but look closer (as I did last year on a very touristy trip through the state while staying in Memphis) and you'll see other traits such as their blues heritage, the riverboat culture of the Mississippi Delta, the ornate plantations, and even the fact that they farm fish (aquaculture). Mississippi also has a natural beauty with its swampy magnolia and oak forests that's almost mystical.
The Coen brothers create a strong sense of place in their films and capture that natural beauty out of which tall tales could be spun, the likes of which appear in the travels of Everett, Delmar and Pete. Mississippi is the proud birthplace of the blues in their purest form (as in acoustic, unpolished recordings) which ties into the trademark sound of the inadvertent band formed by the trio known as the Soggy Bottom Boys. In its early form, Blues was almost indistinguishable from something heard in churches which is why it's also appropriate that there's such elaborate religious mythology.
Remember when I talked about the ornate plantations Mississippi was famous for? We see that in the elaborate divide between rich and poor and the class-conscious ex-wife of Everett (Holly Hunter).
Lastly, when I was in Mississippi, a lot of the tourism centered on roads and corridors such as the Blues Highway (running through Clarksdale) or the Natchez Trace and the film emphasizes this geography as well as all the mythical and legendary stuff they encountered was along the road. The character who sold his soul to the devil (Tommy) is even based on a piece of Mississippi folklore about a famous blues guitarist (Robert Johnson) who sold his soul to the devil at the confluence of two major highways in Cleveland, Mississippi.