Preheat the oven to 375°F (190°C).
Heat olive oil in a large skillet over medium heat. Add diced onion and cook until softened, about 4 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Stir in the taco seasoning mix, ground cumin, chili powder, salt, and black pepper. Cook for 1 minute to toast the spices.
Add the shredded chicken, black beans, corn, and salsa to the skillet. Stir well to combine and heat through for 3-4 minutes. Remove from heat.
In a medium bowl, mix the sour cream with half of the shredded cheddar cheese and half of the Monterey Jack cheese.
Lightly grease a 9×13 inch casserole dish.
Spread a thin layer of the chicken mixture evenly in the bottom of the casserole dish.
Layer half of the tortilla strips over the chicken mixture.
Spread half of the sour cream and cheese mixture over the tortilla strips.
Repeat layering with the remaining chicken mixture, tortilla strips, and sour cream and cheese mixture.
Sprinkle the remaining shredded cheddar and Monterey Jack cheese evenly on top.
Cover the casserole with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly and the tortilla strips are crispy.
Remove from oven and let the casserole rest for 5 minutes before serving.
Garnish with chopped fresh cilantro before serving.