Cooking the chicken breasts in canned broth doubles up on the chicken flavor for this south-of-the-border soup.
Place broth in large saucepan or Dutch oven; add chicken. Bring to boiling. Reduce heat and simmer, covered, about 15 minutes or until chicken is tender and no longer pink. Remove chicken from broth. Let stand until cool enough to handle.
Skin, bone, and finely shred chicken; set aside. Discard skin and bones. Strain broth through large sieve or colander lined with two layers of 100-percent-cotton cheesecloth. Skim fat from broth; set broth aside.
In same saucepan cook onion, cumin, and garlic in 1 tablespoon hot oil until onion is tender but not brown. Stir in strained broth, undrained tomatoes, tomato sauce, chili peppers, cilantro, and oregano. Bring to boiling. Reduce heat and simmer, covered, for 20 minutes. Stir in chicken; heat through.
Cut tortillas in half, then cut them crosswise into 1/2-inch-wide strips. In a heavy medium skillet heat 1/4 inch of oil. Fry strips in hot oil, half at a time, about 1 minute or until crisp and light brown. Remove with a slotted spoon; drain on paper towels.
Divide tortilla strips among 4 bowls. Ladle soup over tortilla strips. Sprinkle each serving with cheese. Serve immediately. Makes 4 servings.