Using a large skillet melt butter. Sauté the bell peppers and onions until lightly softened, about 3-5 minutes. Add the garlic and cook additional 30 seconds.
Stir in the sour cream, garlic powder, chilies, and enchilada sauce. Add salt and pepper to taste. Add 1 cup of sauce to shrimp mixture, stir to combine.
Assemble the enchiladas. Add 1/3 cup shrimp mixture to a flour tortilla, roll tightly and place seam side down in the baking dish. Repeat with remaining tortillas.