In a large saucepan, cook beef over medium heat until no longer pink; drain. Add the salsa, mayonnaise and chili powder.
In an ungreased 2-qt. baking dish, layer half of the meat mixture, chips and cheeses. Repeat layers. Bake, uncovered, at 350° for 20-25 minutes or until heated through. Just before serving, top with tomato and lettuce.