Heat a very large skillet over medium-high heat and add the olive oil. When the skillet is hot but not smoking, add the onions and red and orange peppers. Stir-fry for 3-5 minutes until they begin to soften. Remove and set aside, covering to keep warm.
Add another tablespoon of oil to the skillet. Add the chicken and brown on both sides, about 3-4 minutes per side. Once browned, add the enchilada sauce, chili powder, smoked paprika, cumin, salt, pepper, cayenne, garlic powder, and onion powder. Bring to a boil.
Reduce the heat to a simmer and cook for 10-15 minutes until the chicken is cooked through and shreds easily.
Meanwhile, in a medium saucepan, bring chicken broth and milk to a boil. Slowly whisk in the polenta and cook until soft and thick, about 15-20 minutes. Stir in cheddar cheese and butter, seasoning to taste.
Remove the chicken from heat, shred it in the sauce, and toss in the black beans to warm through.
To assemble bowls, place a serving of polenta in each, topping with peppers and chicken. Finish with avocado, queso fresco, cilantro, and crushed tortilla chips.