In a large skillet, cook beef over medium heat until no longer pink; drain. Add spaghetti sauce and taco seasoning; simmer, uncovered, for 10 minutes.
Meanwhile, for cheese sauce, melt butter in a large saucepan. Stir in flour, garlic powder and pepper. Gradually add milk. Bring to a boil. Cook and stir for 2 minutes or until thickened and bubbly. Add American cheese; cook and stir until melted. Remove from the heat.
On eight plates, layer the rice, lettuce, tomatoes, onion, beans, cheddar cheese and tortilla chips. Top with meat mixture, sour cream and cheese sauce.