Preheat oven to 375°F and spray a 9x13-inch baking dish with cooking spray.
In the prepared dish, combine uncooked rice, chicken broth, cream of chicken soup, sour cream, 1 cup of cheddar cheese, garlic powder, onion powder, salt, and pepper. Stir well.
Add chicken pieces and broccoli florets to the mixture, distributing evenly throughout the dish.
Cover tightly with aluminum foil and bake for 40 minutes.
Remove foil, sprinkle remaining 1 cup of cheddar cheese on top, and bake uncovered for 5 more minutes until cheese is melted and bubbly.
Let casserole rest for 5 minutes before serving to allow the rice to absorb any remaining liquid.