Combine Cream Cheese and Mayonnaise: In a large mixing bowl, beat together the softened cream cheese and mayonnaise until smooth and well combined.
Add Cheeses and Peppers: Stir in the shredded cheddar cheese, Monterey Jack cheese, chopped jalapeños, and green chilies to the cream cheese mixture. Mix well.
Season: Add garlic powder and salt to taste. Adjust the seasoning according to your preference.