From Argentina (and Uruguay), I've rented through both international chains (Hertz, Avis, etc.) and local agencies - none have ever required an Int'l license.

I also had a minor fender-bender getting out of a parking garage in Mar del Plata last year (no other vehicles involved, no police required). My rental car coverage from MasterCard reimbursed the repair charges billed by Avis without any issues whatsoever (phoned in claim, filled out a form when it came in the mail, received a check a few weeks later).

The only places I've been recently where it appears an international license is required, are Brazil and Ireland.