Preheat the oven to 350°F (175°C). Drain and rinse the beans; thaw corn if frozen. Crush chips lightly, leaving some larger pieces for crunch.

Heat a skillet over medium-high heat. Add the ground beef or turkey and cook, breaking it up, until no longer pink, about 6–8 minutes. For safety, ground beef should reach 160°F and turkey 165°F. Drain excess fat if needed.

Stir in the taco seasoning and 1/4 cup water (or the amount called for on the packet). Add the canned diced tomatoes with green chiles, black beans, and corn. Simmer for 2–3 minutes until heated through and combined. Taste and adjust salt/pepper.

In a 9x13-inch baking dish, spread half the meat mixture in an even layer. Sprinkle 1 cup of crushed tortilla chips over the meat. Top with remaining meat mixture, then sprinkle the shredded cheese evenly on top, finishing with any remaining chips for extra crunch if desired.

Place in the preheated oven for 12–18 minutes, until cheese is melted and the casserole is bubbling around the edges. If you like a golden top, broil for 1–2 minutes, watching closely to avoid burning.

Let the casserole rest for 5–10 minutes so it sets up. Top with sour cream, sliced avocado, chopped cilantro, and a squeeze of lime if desired.