For the casserole: Preheat the oven to 375°F.
In a large Dutch oven, heat the oil over medium heat. Add the bell pepper, onion, poblano, and garlic. Cook, stirring occasionally, until the vegetables are softened, 10 to 12 minutes. Add the ground beef and taco seasoning packet. Cook, stirring often to break into small crumbles, until browned, 6 to 8 minutes. Add the canned tomatoes and green chiles, black beans, corn, and salt, and cook, stirring occasionally, until well combined, about 2 minutes. Remove from the heat.
Lightly grease a 13-by-9-inch baking dish with cooking spray. Arrange the tortilla chips in a slightly overlapping single layer in the bottom of the baking dish (about 35 chips in a layer). Top with about half of the ground beef mixture in an even layer. Sprinkle evenly with half of the cheese. Repeat the layers once, ending with cheese on top. Reserve the remaining chips for serving.
Bake the casserole until the cheese is melted and beginning to brown on top, 16 to 20 minutes. Let cool for 10 minutes before topping and serving.
To serve: Top with shredded lettuce, pico de gallo, avocado, cilantro, sour cream, black olives, and hot sauce. Serve with extra tortilla chips.