Defrost the frozen corn and then drain and pat it dry with paper towels or a clean kitchen towel to remove excess moisture.
Drain the can of chopped green chilies.
Dice the ½ red bell pepper, chop the bunch of green onion, and dice the fresh jalapeño if using (remove seeds if you want less heat).
In a large bowl, combine the 1 cup mayonnaise and 1 cup sour cream until smooth.
Stir in the 1 teaspoon cumin and 1/8 teaspoon cayenne pepper into the mayo–sour cream mixture.
Add the 2–3 cups defrosted corn, drained chopped green chilies, diced red bell pepper, chopped green onion, diced jalapeño (if using), and 2 cups shredded sharp cheddar cheese to the bowl.
Mix everything thoroughly until evenly combined.
Cover the dip and refrigerate for about 1 hour to let the flavors meld and to firm up slightly.
After chilling, give the dip a final stir and serve with tortilla chips.