Preheat oven to 350°F (175°C).
In a large mixing bowl, combine shredded chicken, chopped onion, chopped green bell pepper, cream of mushroom soup, cream of chicken soup, diced tomatoes with green chilies (including liquid), diced green chilies, chicken broth, chili powder, ground cumin, garlic powder, and black pepper. Stir until well combined.
Lightly spray a 9×13-inch baking dish with cooking spray.
Spread one-third of the tortilla strips evenly on the bottom of the prepared baking dish.
Spoon one-third of the chicken mixture over the tortilla layer and spread evenly.
Sprinkle one cup of shredded cheddar cheese over the chicken mixture.
Repeat layering two more times, finishing with cheese on top.
If preparing as a freezer meal, cover the casserole tightly with aluminum foil and freeze for up to 3 months.
To bake from frozen, remove foil and bake covered at 350°F (175°C) for 45 minutes, then uncover and bake an additional 10-15 minutes until cheese is bubbly and golden.
If baking immediately, cover casserole with foil and bake at 350°F (175°C) for 35 minutes, then uncover and bake an additional 10-15 minutes until cheese is melted and bubbly.
Let casserole rest for 5 minutes before serving.