The other risk of getting a USA-Switzerland-Italy ticket, planning to get off the plane in Switzerland, is that the airline doesn't promise to take you to Switzerland unless it's specifically listed as a stop-over. It promises to get you to Italy somehow. If anything goes wrong with its schedule, weather, mechanical, involuntary bump or anything else, they may find it easiest to get you to Italy via (say) London or even a non-stop from a US gateway. If that happens, there isn't a thing you can do about it other than staying where you are, assuming your citizenship and entry status permit this.