In 5-quart Dutch oven, cook beef and onion over medium heat 8 to 9 minutes, stirring occasionally, until brown; drain. Stir in taco seasoning mix, water, chiles and cumin; stir until well blended. Cook 1 to 2 minutes or until slightly thickened. Add tomatoes, tomato sauce, 1 1/2 cups of the shredded cheese and the spaghetti; stir well to blend. Pour mixture into baking dish. Scatter cheese cubes throughout casserole, and push gently into pasta mixture. Top with remaining 1/2 cup shredded cheese.