In a 6 quart or larger slow cooker, stir together the chicken, corn, broth, tomatoes with liquid, onion, sugar, chili powder, garlic and salt.
Cook, covered, on low for 6 to 8 hours or on high for 3 to 4 hours.
Meanwhile, preheat the oven to 350°F.
Arrange the tortilla stips in a single layer on a baking sheet.
Bake for 8 to 10 minutes, or until crisp.
Transfer the baking sheet to a cooling rack.
Let the strips stand for about 15 minutes, or until cool.
Transfer to an airtight container and set aside.
When the soup is ready, transfer 1 cup to a food processor or blender.
Stir in the tortilla pieced (not the strips you baked but the 1 tortilla that was just torn into pieces).
Let the mixture stand for 1 minute so the tortilla pieces soften.
Process until smooth.
Stir the mixture into the soup.
Stir in the cilantro.
Ladle the soup into bowls.
Sprinkle with the avocado, bell pepper and reserved baked tortilla strips.
Notes
Cook's Tip: Adding the processed soup and tortilla mixture to the rest of the soup gives the finished product more body and distributes the tortilla flavor.