Place the chicken breasts at the bottom of the crockpot.
Add the red enchilada sauce, diced tomatoes, green chilies, onion, garlic, chicken broth, cumin, chili powder, salt, and pepper to the crockpot.
Stir to combine the ingredients.
Cover and cook on high for 4 hours or low for 8 hours until the chicken is cooked through and tender.
Remove the chicken from the crockpot and shred it using two forks. Return the shredded chicken to the crockpot.
Stir in the shredded cheddar cheese until melted and well combined.
Taste and adjust seasoning if needed.
Serve hot, garnished with fresh cilantro, sliced avocado, and a dollop of sour cream.