Preheat oven to 350 degrees. Drain the asparagus, saving 2/3's of the juice. Make an even layer of asparagus in casserole dish. Cover with even layer of American cheese.
In small saucepan, heat the asparagus juice and the butter. Slowly add 6 tablespoons flour, while stirring continuously. As sauce begins to thicken, remove from heat. Spread sauce over cheese. Then cover with crushed Cheez-its and bake for 25 to 30 minutes. Cheez-its may be used heavily (about 1/2 of 1 lb. box) or lightly, according to taste.