Preheat the oven to 350°F (175°C) and lightly spray a 9x13-inch baking dish with cooking spray; set aside.
Bring a large pot of salted water to a boil and cook the angel hair pasta according to package directions until al dente; drain well in a colander.
In a large mixing bowl, combine the chopped cooked chicken, cream of chicken soup, sour cream, onion powder, garlic powder, undrained Rotel, and 1/2 cup of the shredded cheddar; stir until evenly mixed.
Add the drained pasta to the chicken mixture and toss gently to coat, then spread the mixture evenly into the prepared baking dish.
Sprinkle the remaining shredded cheddar evenly over the top, then spread the French fried onions over the cheese.
Bake in the preheated oven for 25 to 30 minutes, until the casserole is bubbly and the topping is golden; remove and let rest a few minutes before serving.