Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish with cooking spray or a thin layer of oil. This prevents sticking and makes cleanup easier.
Bring a large pot of salted water to a boil and cook the spaghetti according to package directions. Make sure the pasta remains slightly firm because it will continue cooking in the oven. Drain well and set aside.
In the same pot, combine cream of chicken soup, Rotel tomatoes with their juices, sour cream, chicken broth, garlic powder, onion powder, salt, black pepper, and red pepper flakes. Stir until the mixture becomes smooth and fully blended.
Fold the cooked spaghetti into the creamy sauce. Add the shredded chicken and mix thoroughly so every strand of pasta gets coated. This ensures a flavorful bite every time.
Pour the prepared spaghetti mixture into the greased baking dish. Spread it evenly using a spoon or spatula. An even layer helps the casserole bake consistently.
Sprinkle half of the cheese into the mixture and stir gently. Then top the casserole with the remaining cheese to create a delicious golden and bubbly finish.
Cover the baking dish with foil and bake for about 20 minutes. Remove the foil and continue baking for another 5 to 10 minutes until the cheese is melted and lightly golden.
Remove the casserole from the oven and allow it to rest for a few minutes. Sprinkle freshly chopped parsley over the top before serving for added freshness and color.