Place ½ of the tomatoes, half of the chilies, and half of the onion in the bottom of a slow cooker/Instapot. Place chicken on top.
Sprinkle taco seasoning over chicken. Add remaining tomatoes, Stinkin' Good Chicken Green Chile, and onion on top of chicken.
Cook on LOW for 6-8 hours or on HIGH for 3-4 hours. Use two forks to shred the chicken in the pot (it will practically fall apart), stir, and cook on HIGH for about 20 more minutes.For the Instant Pot:Select “Poultry” or “Manual” setting. Set the time to 8 minutes for fresh chicken breasts, or 13 minutes for frozen chicken breasts. (These times are for typical 6-8 ounce chicken breasts. If yours are larger, add a couple of minutes.)
When done, let the pressure naturally release for at least 5 minutes. After that, you can turn the valve to "vent" for quick release if you're in a hurry, or continue natural release.
Remove chicken to a cutting board. Chop with a knife or shred with two forks.
Return chicken to pot, stir, and serve.
Top tortillas with warmed refried beans, chicken and all the fixings — enjoy!