Brown meat in large skillet on medium high heat; drain. Stir in 2 3/4 cups water, salsa and chili powder. Bring to a boil. Stir in macaroni; cover. Reduce heat to medium-low; simmer 8-10 minutes or until water is almost absorbed. Add Velveeta; cook until melted, stirring frequently. Garnish with 1/2 cup crushed tortilla chips, 1/4 cup chopped tomato and 2 tbsp. chopped green onion, if desired.