Cook the macaroni noodles according to the package directions. Drain and set aside.
In a large mixing bowl, stir together the Cubed American cheese and cooked noodles until well combined and the American cheese has melted.
Add the seasonings; salt, pepper, garlic powder, onion powder and stir to combine.
Add warm milk and stir to coat noodles with the cheese sauce.
Add ½ of the shredded cheeses to the bowl and stir to combine everything.
After the meatloaf has baked for 40-45 minutes, remove it from the oven.
Drain off any excess fat that has accumulated along the edges of the casserole dish.
Spread the Mac & Cheese mixture evenly over the top of the meatloaf.
Top with the remaining shredded cheeses and return the casserole dish to the oven.
Bake for another 20-25 minutes or until the Mac & Cheese is hot and bubbly and the cheese topping is completely melted and starting to brown along the edges.
Turn oven temperature to "broil" and continue to cook until cheese topping is lightly browned. Keep a close eye on it so it doesn't burn.
Remove casserole from the oven and allow it to rest for 5-10 minutes before cutting into it and serving.