Preheat the oven to 350°F. Spray a 9×13-inch baking dish with nonstick spray.
Crush the chips: 2 cups finely (crumb-like) and 1 cup loosely (bigger pieces). Set aside.
In a large skillet over medium-high heat, cook the ground beef and onion until the beef is almost done. Drain excess grease if needed.
Add the garlic and cook for 1 minute.
Stir in the taco seasoning and water. Simmer for 1 to 2 minutes, until slightly thickened.
Add the black beans, pinto beans, frozen corn, diced tomatoes with green chilies (with liquid), and salsa. Stir and cook 2 to 3 minutes.
Reduce heat to low. Add the cream cheese and stir until melted. Remove from heat and stir in the sour cream and 2 cups of shredded cheese.
Stir in 2 cups of finely crushed chips.
Spread the mixture into the prepared baking dish. Bake for 20 minutes.
Remove from oven. Top with remaining 1 cup cheese and 1 cup loosely crushed chips. Bake 5 to 7 minutes, until cheese is melted.
Rest 5 to 10 minutes before serving. Add toppings and enjoy.