Heat the oven to 350 degrees F. Arrange the tortilla strips on 2 baking sheets.
Bake for 10 minutes or until the tortilla strips are crisp and lightly browned. Reserve 5 tortilla strips.
Heat the oil in a 12-inch skillet over medium-high heat. Add the onion and oregano and cook for 2 minutes, stirring occasionally. Add the garlic and cook and stir for 1 minute.
Stir in the soup and water and heat to a boil. Reduce the heat to medium. Cook, uncovered, for 5 minutes. Stir in the chicken and black pepper and cook until the mixture is hot and bubbling.
Stir in the remaining tortilla strips and cook until the mixture is hot. Remove the skillet from the heat. Sprinkle the chicken mixture with the cheese. Top with the reserved tortilla strips and the cilantro, if desired. Serve with the lime wedges.