Defining southern culture is not as simple as some folks in this thread imply.
It's not a political formula. It's not the Civil War, nor that conflict's antecedents.
It's not just accents, though accents are a flag (or a set of flags).
Being Southern is about how you interact with people. It's about what you do on Sundays. How you relax with friends on Friday and Saturday nights. What kinds of music you tend to like most. How much time you spend outdoors when you have free time. How important you consider loyalty to your team, your tribe, your community. Whether you take care of your parents as they get older.
Sure, Southerners are recognized by our accents, sometimes our clothing, even by the slower pace of living at times. But those are surface ripples. What's important is deeper down.
Southerners are no more or less racist than Northerners or folks from anywhere else. No more or less misogynist. We are more religious, but are no more likely to be extremists. Those are simple insults Northerners sometimes use to forgive or conceal their own sins.
I do think we are kinder people. My friends from New York City and Long Island used to love to say that Southerners are kind to your face, but mean behind your back, while New Yorkers are the opposite. This is wrong. Southerners are simply kinder, in my experience.
Southerners aren't defined by how ferociously we fight. I've known fellas from Boston and Baltimore who are just as quick to anger, and just as tenacious about it. But Southerners--and Tennesseans in particular--are quicker to jump into a fight to help a friend out, even when they aren't directly involved. From what I've seen, Northerners sit back a while longer to get a better feel for the odds and circumstances. They can argue that's smarter, but it's not as loyal to a friend. For sure.
I could go on for pages about what a Southerner is, and how we compare to folks from the North. I've spent a lifetime around a lot of the latter, and lived in several northern and western places.
Simple truth is, you know when you're with a Southerner. We're unique, even if our accents are hugely different from Coastal Carolina to Nashville to New Orleans...and yes, to Houston.
Go Vols!