Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes; drain.
Melt butter in a large pot over medium-low heat. Slowly add flour to butter, whisking constantly; cook until brown and the mixture no longer smells of flour, about 5 minutes. Pour 1 cup milk into the flour mixture, whisking continually until fully incorporated, about 45 seconds; repeat twice. Add remaining 3 cups milk to the mixture, whisking to incorporate. Stir mustard powder, onion powder, and cayenne pepper into the mixture; season with salt and black pepper.
Reduce heat to low. Cook sauce, whisking frequently, until it begins to thicken, about 10 minutes. Add about half the package of shredded Cheddar cheese; stir continually until the cheese melts completely. Repeat with remaining half package of Cheddar cheese and the American cheese, about 4 ounces at a time. Once cheese is entirely incorporated, remove sauce from heat.
Stir drained macaroni into the cheese sauce to coat. Divide macaroni between two 9x13-inch baking dishes.
Mix crushed potato chips, 1 cup shredded Cheddar cheese, and Parmesan cheese in a bowl. Top the macaroni with the potato chip mixture evenly. Spray the potato chip mixture with cooking spray.
Bake in preheated oven until the crust is golden brown and the sauce is bubbling, 35 to 45 minutes.