Preheat the oven to 350°F (175°C).

In a large skillet, sauté the onion and bell pepper until softened.

In a mixing bowl, combine the cooked chicken, cream of chicken soup, diced tomatoes with green chilies, garlic powder, chili powder, salt, and pepper.

Layer half of the tortilla strips in the bottom of a greased casserole dish.

Spread half of the chicken mixture over the tortilla layer.

Sprinkle a layer of cheese over the chicken.

Repeat the layers with the remaining tortilla strips, chicken mixture, and cheese.

Cover the casserole with aluminum foil and bake for 25 minutes.

Remove the foil and bake for an additional 15 minutes until cheese is bubbly and golden.

Let the casserole cool for 10 minutes before serving.