Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish with cooking spray or butter.

In a large skillet, heat the olive oil over medium-high heat. Add the ground beef and chopped onion. Cook, breaking up the meat with a spatula, until the beef is fully browned and the onion is translucent, about 5-7 minutes. Drain off any excess grease from the skillet.

Reduce the heat to medium. Stir in the taco seasoning packet, water, and the entire can of diced tomatoes and green chiles (do not drain). Bring the mixture to a simmer and cook for 2-3 minutes, allowing the sauce to thicken slightly.

In a separate medium bowl, combine the softened cream cheese, sour cream, drained corn, and 1 cup of the shredded Mexican cheese blend. Stir until all ingredients are evenly mixed.

Spread the seasoned beef mixture evenly across the bottom of the prepared baking dish. Next, carefully spread the creamy corn mixture in an even layer over the beef.

Sprinkle the remaining 1 cup of shredded cheese over the creamy layer. Finally, top the entire casserole with the coarsely crushed tortilla chips.

Bake in the preheated oven for 20-25 minutes, or until the casserole is hot and bubbly and the cheese is completely melted. The chips on top should be lightly golden.

Remove from the oven and let the casserole rest for 5-10 minutes before serving. This helps it set, making it easier to cut and serve. Garnish with fresh cilantro, diced tomatoes, green onions, and a dollop of sour cream, if desired.