I own a home and car in Italy and have never had an issue with needing an IDL. I used to get them , but finally gave up. You do not need it to rent the car . If you get in an accident , the rent a car company provides forms to be filled out , found in the glove box of the car, and only an original dl's info may be entered. Any other party would laugh at an IDL.
I have also found that Caribineri , Poliza Stradale , Vigili , could care less about them , and usually leave you alone when they find out you are American. perhaps the one lonely cop may give you a lecture. ( As in Hybrid case.)
Many rent a car companies , if you get a ticket or are in an accident , charge an administrative fee , for processing any claims or fines. Do not leave a valid credit card with them to charge anything to. I always use a low limit card , and cancel it , after returning the car.
Save your time and money. You do not need it. BTW: Argentine dl's are valid in Italy (and Spain).