Heat the oil in a 4-quart Dutch oven over medium-high heat until shimmering. Add the onion and cook until beginning to brown and soften, about 5 minutes. Add the ground beef, taco seasoning, and garlic and cook, breaking up the meat into small pieces with a wooden spoon, until browned and no pink remains, 5 to 7 minutes.

Add the beans, salsa, and macaroni and stir to combine. Pour in the chicken broth, cover, and bring to a boil over medium-high heat. Uncover and cook, stirring occasionally, until the pasta is tender and most of the liquid is absorbed, about 15 minutes. Meanwhile, arrange a rack about 6 inches from the broiler (make sure the pot will fit). Heat the broiler to high.

Stir the corn and 1 1/2 cups of the cheese into the pasta. Sprinkle the remaining 1/2 cup of cheese over the top. Broil until the cheese melts and turns golden-brown, 2 to 3 minutes. Cool for 5 minutes before serving with your favorite taco fixings.