Put the chicken breasts in a 6-quart slow cooker and season them with the salt, chili powder and cumin.
Add the crushed tomatoes, black beans, corn, green chiles, onion and broth.
Cover and cook on low until the chicken reaches 165°F and the onion is tender, 4 to 4 1/2 hours.
Transfer the chicken to a bowl and shred it into thick strands.
Return the chicken, stir in the lime juice and let the soup stand covered for 10 minutes.
Ladle into bowls and add the crisp tortilla strips immediately before eating.