Okay. This has been one of my favorite food posts so far because 1) I HEART food and 2) I am from the South. Several good points have been made already, like cornbread is NOT sweet (very important) but several misconceptions: GREENS is a generic term that refers to any greens- collards, kale, mustard, etc.
Collards are not bitter if cooked properly and picked at the right time. Mustard greens are very bitter and an acquired taste for most. You must add hot sauce and a splash of pepper vinegar to any greens for an authentic experience.
Southern food (soul food) is very much based on African and Central/South American food- that is, heavy on the beans, pork, hot sauce and tomatoes. The important thing to remember is that vegetables are not necessarily vegetarian, as most are cooked with fatback or saltpork for a long time until they are stew-like.
Several important things left out t hat you should try: hushpuppies (fried dough that is also NOT sweet- eaten with fried fish and incredibly tasty), fried okra (yum), blackeyed peas, fried green tomatoes, sweet potato souffle and Brunswick stew. (You get the picture- everything is pretty much deep fried).
Boiled peanuts are one of my all-time favorite foods and you can buy them on the side of the road in the early fall from vendors. Kind of like hot, salty chickpeas. Cocacola cake, pineapple upsidedown cake, red velvet cake, pecan pie. Desserts are incredibly sweet and rich. They don't hold back on anything...sugar, fat, salt, spices. Walk into a Southern restaurant and order iced tea and it is invariably sweet (unless you request unsweetened, which makes you suspicious).
Barbeque is another subject unto itself, but the person from South Carolina covered that pretty well with the mustard vs. tomato-based variations. I prefer the tomato myself.
Southern food is incredibly rich and usually requires a long nap afterward if you eat a traditional menu. Not for everyday, of course, but damn tasty every once in a while.
Oh, one other weird SOuthern food tradition...salt on fruit (like the Latin Americans). I can't eat an apple or a pear or watermelon without salt on it. Makes the fruit sweeter by contrast.