1. Warm vegetable oil in a large saucepan over medium heat. Add onion and cook, stirring, until softened, about 5 minutes. Add garlic, chili powder and crushed red pepper; cook mixture for 30 seconds, stirring.
2. Stir in broth and tomatoes and bring to a boil. Reduce heat and simmer 15 minutes. Stir in chicken and cook until heated through, 1 to 2 minutes. Season with salt. Stir in cilantro. Divide tortilla chips among 4 shallow soup bowls. Ladle soup on top of chips and serve immediately.