Preheat oven to 350ºF (177ºC). Boil spaghetti in a large pot until al dente, according to package directions (break the noodles in half if desired). Drain and set aside.
In the large pot, heat the Rotel, cream of mushroom soups, half of the shredded cheddar (1 cup), Velveeta, onion powder, garlic powder, and salt on medium to medium-high heat until the cheese melts, stirring constantly. Turn off the heat.
Stir in the shredded cooked chicken breast and cooked spaghetti noodles a little bit at a time.
Pour the mixture into a lightly greased 9x13 baking dish. Top with the remaining cheddar cheese. Bake for 25 to 30 minutes or until heated through.
