Check out The South -- the coastal area along the Gulf of Mexico. Everyone is obese. Food is great and cheap. Wonderful cross pollination of Mexican, French, Cajun, Vietnamese, English, German, Czech food going on down there. Best of all worlds!

Taco Bell

Tasty; notorious for destroying yous stomach, and later, your toilet. Fair warning. Keep in mind we share a border with Mexico, so we've got pretty decent options for Mexican food. If you're in an area with food trucks, those are consistently the best for some reason.

Wendys

If I blindfolded you and fed you a Wendy's burger and told you it was McDonalds, you wouldn't question it. Until the cashier tells you how much your meal costs... I recall them being just expensive McDonalds.

Jack in the Box

Been ages since I've been there... can't remember if it was them or Hardees/Carl's Jr, but I recall their criscut fries being better than the average fast food.

In n out Burger

I know these are fighting words, but: they're trash. In n' Out, Hard Rock Cafe, and Five Guys are like the trinity of overrated fast food: poorly executed attempt at feeling like a fancy diner, but the food - the meat in particular - is absolutely flavorless. I'd point you instead to the regional chains like Culver's or Braum's.

...and I'd guess this is true of most largish cities around the world vs being uniquely American, but they tend to have districts that lean heavily toward or are outright dedicated to a specific culture or group, and the restaurants in those area are consistently among the best. Like if you want Vietnamese food, don't just hit a pho chain in a random strip mall - find the Asian district, and look for the oldest, most beat-up looking hole-in-the-wall restaurant you can find there, and you'll get the best pho you've ever had.