Preheat oven to 350. Prepare a 2-quart casserole dish with cooking spray; set aside. In a small bowl, lightly combine stuffing and broth. Let stand five minutes, or until broth is absorbed. Set aside half cup mixture. Press remaining mixture into prepared dish to form a crust. Bake for 15 minutes. Meanwhile, in a large saucepan, cook chicken and onions until chicken is no longer pink. Add chili powder, garlic powder, corn kernels, half cup cheese, salsa, and reserved stuffing mixture. Mix well. Spoon into baked layer. Sprinkle top with remaining cheese. Bake for 20 minutes, or until heated through.