Heat the oven to 350°F and lightly grease a 9-by-13-inch baking dish. Set the dish aside while you prepare the vegetables and creamy sauce.

Melt the butter in a large skillet or Dutch oven over medium heat. Add the chopped onion and green bell pepper, then sauté for about 5 minutes, stirring occasionally, until the vegetables soften.

Add the minced garlic to the softened vegetables and cook for about 30 seconds. Stir continuously so the garlic becomes fragrant without browning.

Stir in both cans of condensed cream of chicken soup, the undrained tomatoes with green chiles, chili powder, salt, and black pepper. Heat the mixture until it is smooth and hot, adding 1/2 to 1 cup chicken broth only if the sauce seems unusually thick.

Layer approximately one-third of the corn tortilla strips across the bottom of the prepared baking dish. Arrange them in an even layer so every serving gets some tortilla texture.

Add half of the cooked chicken, about one-third of the soup mixture, and one-third of the shredded cheddar cheese. Spread the sauce gently rather than pressing down on the tortillas.

Repeat the layers with another one-third of the tortilla strips, the remaining chicken, another one-third of the sauce, and another one-third of the cheese. Finish with the remaining tortilla strips, sauce, and cheddar on top.

Bake the casserole uncovered at 350°F for 35 to 40 minutes. It is ready when the sauce bubbles around the edges and the cheese is melted, lightly browned, and glossy.

Let the baked casserole stand for 10 minutes before serving. This short rest allows the layers to set and gives the tortillas time to absorb some sauce without becoming completely mushy.