Preheat the oven to 350°F (175°C).
Cook the spaghetti according to package instructions until al dente.
In a large mixing bowl, combine the cooked spaghetti, shredded chicken, cream of mushroom soup, milk, garlic powder, onion powder, and mixed vegetables.
Add salt and pepper to taste, adjusting as necessary.
Transfer the mixture into a greased 9x13 inch baking dish.
Sprinkle shredded cheddar cheese evenly over the top.
For added crunch, top with breadcrumbs if desired.
Bake in the preheated oven for 30-35 minutes, or until bubbly and golden brown.
Remove from the oven and let it sit for 5-10 minutes before serving.
