Spray 5-quart slow cooker with cooking spray. Place chicken breasts in slow cooker. Cover with tomatoes, taco seasoning mix and chilies. Cover; cook on High heat setting 3 1/2 hours or on Low heat setting 7 hours. Shred chicken. Place cream cheese over chicken. Cover; cook 30 minutes longer.
Meanwhile, heat tortillas and prepare toppings. Stir chicken mixture; portion into tortilla bowls, and serve with toppings.