Preheat the oven to 350°F and spray a 9-inch square baking dish with nonstick cooking spray.
Bring a large pot of salted water to a boil; cook the spaghetti according to package directions until al dente. Drain and set aside.
Cut the chicken into bite-size pieces and toss with 1 tablespoon taco seasoning.
In a large skillet, melt 1 tablespoon butter over medium-high heat. Add the seasoned chicken, 1/2 teaspoon garlic powder, and 1/2 teaspoon onion powder. Cook, stirring occasionally, until the chicken is cooked through and any liquid has evaporated.
Reduce heat to low and stir in the cream of chicken soup, cubed Velveeta, and the undrained can of Rotel. Stir constantly until the cheese has melted and the sauce is smooth.
Add the cooked spaghetti to the skillet and toss gently to combine so the pasta is evenly coated with the sauce.
Pour the mixture into the prepared baking dish, sprinkle 1 cup shredded cheddar cheese over the top, and bake for 25 to 30 minutes until heated through and the cheese is melted.
