01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with butter or nonstick spray.
02 - Bring a large pot of salted water to a boil. Cook the macaroni according to package directions until al dente, then drain and set aside.
03 - In a large skillet over medium heat, cook ground beef until fully browned. Drain excess fat from the skillet.
04 - Add chopped onion and diced red bell pepper to the skillet with beef. Sauté for 3 to 4 minutes until vegetables are softened.
05 - Stir in taco seasoning, black beans, diced tomatoes with green chilies, and frozen corn. Cook for 2 to 3 minutes until heated through, then remove skillet from heat.
06 - In a saucepan over medium heat, melt butter. Whisk in flour and cook for 1 minute. Gradually add milk while whisking continuously until slightly thickened, about 2 to 3 minutes.
07 - Reduce heat to low. Add cream cheese and 1 1/2 cups of the shredded cheddar cheese to the sauce. Stir until cheese is fully melted and sauce is smooth.
08 - In a large mixing bowl, combine cooked macaroni, beef and vegetable mixture, and cheese sauce. Mix thoroughly and season with salt and black pepper.
09 - Transfer mixture into prepared baking dish. Sprinkle remaining 1/2 cup shredded cheddar cheese and crushed tortilla chips over the top.
10 - Bake uncovered for 20 to 25 minutes until casserole is bubbly and cheese topping is golden brown. Allow to cool for 5 minutes before serving.