Heat oil in a large vessel over medium heat. Add chicken and cook until no longer raw, about 15 minutes. Reduce heat to medium low and transfer chicken to a plate and shred.
Add remaining ingredients and shredded chicken back to the pot and stir. Cover and cook until thick and bubbly, about 1 hour.
Chili powder refers to the spice blend made up of paprika, cumin, etc.; It is not meant to be confused with cayenne or red chili powder.