Heat oven to 425°F. Spray 3-quart casserole with cooking spray. Cook and drain macaroni as directed on package, using minimum cook time; cover to keep warm.
Meanwhile, in Dutch oven or 3-quart saucepan, melt 1/3 cup butter over medium-low heat. Stir in flour, salt and pepper. Cook and stir until smooth and bubbly. Gradually add milk and water, stirring constantly, until mixture boils and thickens. Add 4 cups of the cheese; stir until cheese is melted.
Add cooked macaroni to cheese sauce; toss to coat completely. Stir in chicken and chiles. Spoon mixture into casserole. Sprinkle with remaining 1 cup cheese.
In small bowl, mix bread crumbs and melted butter. Sprinkle over macaroni mixture.
Bake uncovered 25 to 30 minutes or until browned and bubbly.