Heat vegetable oil in a large heavy bottom pot over medium heat.
Stir in onion and bell pepper and cook until softened, about 5 minutes.
Add cumin, chili powder, and salt. Stir to coat the veggies in seasoning, and cook until fragrant (about 2 minutes).
Add the enchilada sauce, chicken broth, diced tomatoes, and chicken. Stir to incorporate.
Bring soup to a boil, then reduce to a simmer.
Simmer for 30-40 minutes. This will vary depending on how thick your chicken is.
Use tongs to remove chicken from the soup and check the internal temp (should be 165 F). If not fully cooked, toss chicken back into the pot and continue to simmer. Once fully cooked, allow it to cool on a plate.
Stir in sour cream and cheddar.
Shred the chicken, and add it back to the soup.
Stir in cilantro and green onions.
Top with toppings of choice, and enjoy!