In a large mixing bowl, combine the shredded chicken, softened cream cheese, green chilies, garlic powder, ground cumin, Monterey Jack cheese, and a pinch of salt and black pepper. Use a spatula to mix everything together until well combined.
Warm the tortillas slightly in the microwave or on a skillet to make them pliable.
Spread a thin layer of the red enchilada sauce on the bottom of your casserole dish. Take a tortilla and add a generous amount of the chicken mixture in the center. Roll the tortilla tightly around the filling and place it seam-side down in the casserole dish.
Once all the enchiladas are assembled in the dish, pour the remaining red enchilada sauce over the top. Sprinkle the Mexican blend cheese evenly over the sauce.
Cover the dish with aluminum foil and bake in the preheated oven for 20 minutes. After 20 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove the enchiladas from the oven and let them cool for a few minutes. Garnish with finely diced red onion, chopped cilantro, and fresh tomatoes before serving.