Place the chicken breasts in the bottom of a 6-quart slow cooker. Season with chili powder, cumin, salt, and pepper.
Add the black beans, corn, enchilada sauce, diced tomatoes, green chiles, poblano pepper, onion and garlic. Pour in the chicken broth and stir to combine.
Cover and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, until the chicken is tender and shreds easily with a fork.
Remove the chicken and shred with two forks. Return the shredded chicken to the slow cooker.
Stir in the chopped cilantro. Taste and adjust seasonings as needed.
Serve hot, topped with shredded cheese, sour cream, avocado, and tortilla strips as desired.