How much passport validity do I need for Italy?

Your passport must be valid for at least three months beyond the date you plan to leave the Schengen Area, and it must have been issued within the previous ten years. That second rule catches people out: a passport renewed early can carry extra months that push its issue date past ten years, and it stops being valid for Schengen entry even though the expiry date looks fine. Check the issue date, not just the expiry. Airlines enforce this at check-in in the US, so a problem surfaces before you board, which is worse than useless when your trip starts that day.