Preheat oven to 375. Prepare a 8 x 30 cm pan with cooking spray; set aside. Return hot macaroni to saucepan. Stir in bacon, chicken, onions, and bell peppers. In a mixing bowl, combine cream of mushroom soup, sour cream, mixed vegetables, garlic powder, and 1 cup cheddar cheese. Spoon half the macaroni mixture into prepared pan. Cover with half vegetable mixture. Repeat layers. Bake, covered, for 30 minutes or until heated through. Top with remaining cheddar cheese. Bake, uncovered, 3 minutes more.