Place the chicken breasts in the bottom of your crock pot. Pour the red and green enchilada sauces over the chicken. Add diced onions, cumin, garlic powder, salt, and pepper. Stir gently to coat the chicken evenly in the sauces and spices. This will help the chicken soak up all the rich enchilada flavor during slow cooking.
Cover the crock pot with its lid and set it to cook—either on low for 6-7 hours or on high for 3-4 hours. When the chicken is fully cooked and tender, it will shred easily. Use two forks to shred it directly in the crock pot, mixing it well with the sauce. This ensures every bite is flavorful and juicy.
Once the chicken is shredded, stir in the drained black beans, corn, diced green chilies, and tortilla strips. The tortillas will absorb the sauce and create a layered, casserole-like texture. Sprinkle 1 cup of the shredded cheese over the top of the mixture to start the melty goodness.
Put the lid back on and continue cooking on low for an additional 30 minutes. This allows all the ingredients to come together and the tortillas to soften. The cheese will begin to melt into the mixture, giving it that irresistible creamy bite.
Just before serving, sprinkle the remaining 1 cup of cheese over the casserole. Let it melt from the residual heat or turn the crock pot to warm for 10-15 minutes if needed. Garnish with fresh cilantro and serve with optional toppings like sour cream, salsa, or guacamole.