Preheat your oven to 375°F (190°C).
In a large mixing bowl, combine the drained corn, undrained diced tomatoes and green chilies, softened cream cheese, sour cream, and mayonnaise. Stir until well combined.
Add 1/2 cup of the shredded cheddar cheese, the Monterey Jack cheese, chopped cilantro (if using), and garlic powder to the mixture. Season with salt and pepper to your liking. Stir everything together until the cheeses are evenly distributed.
Pour the corn dip mixture into an oven-safe skillet or a baking dish. Spread it out evenly.
Sprinkle the remaining 1/2 cup of cheddar cheese over the top of the dip.
Bake for 20-25 minutes, or until the dip is hot, bubbly, and the cheese on top is melted and lightly golden.
Let the dip cool for a few minutes before serving. Serve warm with tortilla chips.