Preheat the oven to 375°F.
Lightly grease an 8×8-inch baking dish or a similar oven-safe dish and set it aside.
If using frozen corn, thaw it completely, drain off all liquid, and pat it dry thoroughly.
If using canned corn, drain it well and pat it dry to remove excess moisture.
In a large bowl, combine the softened cream cheese, sour cream, and mayonnaise.
Stir until smooth and fully blended, using a hand mixer or sturdy spoon.
Add the garlic powder, onion powder, paprika, chili powder, kosher salt, and black pepper.
Stir again until the seasoning is evenly incorporated.
Fold in the drained corn, green onions, and diced red bell pepper.
Stir gently to keep the vegetables intact.
Add 1 1/2 cups shredded cheddar cheese and 3/4 cup shredded Monterey Jack cheese.
Stir until the cheeses are evenly mixed throughout.
Transfer the mixture to the prepared baking dish.
Spread the dip into an even layer.
Sprinkle the remaining cheddar and Monterey Jack cheese evenly over the top.
Bake for 20–25 minutes until the edges are bubbling and the center is hot.
For extra color, broil for 1–2 minutes at the end if desired.
Remove from the oven and let rest for 5–10 minutes before serving warm.