Brown meat in large skillet; drain. Stir in water, ketchup and chili powder. Bring to a boil. Stir in macaroni. Reduce heat to medium-low; cover. Simmer 8 to 10 minutes or until macaroni is tender and water is almost absorbed. Add prepared cheese product, cook until melted, stirring frequently. Garnish with crushed tortilla chips, chopped green onions and tomatoes, if desired.