Preheat your oven to 375°F (190°C).
In a large skillet, brown the ground beef over medium-high heat until fully cooked. Drain the excess grease.
Add the black beans, corn, diced tomatoes, and green chilies to the skillet. Stir in the taco seasoning mix and cook for 5-7 minutes until the vegetables are tender and the flavors are well combined. In a separate bowl, mix together the sour cream and salsa until well combined.
In a 9x13 inch baking dish, spread a layer of tortilla chips on the bottom.
Add a layer of the beef and vegetable mixture on top of the chips.
Pour half of the sour cream and salsa mixture over the beef and vegetable mixture.
Sprinkle a layer of shredded cheese on top of the sour cream and salsa mixture.
Repeat the layers, starting with the tortilla chips and ending with a layer of shredded cheese on top.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Remove the foil and bake for an additional 10-15 minutes until the cheese is melted and bubbly.
Let the casserole cool for a few minutes before serving. Serve with additional tortilla chips and a dollop of sour cream on top, if desired.