If you’re visiting Australia and have a drivers license, from the United States you generally won’t need a driving permit (IDP) to drive there. Your US license should be enough long as its in English. If you have an accredited English translation.
However having an IDP can come in as a form of identification and some car rental companies in Australia may require it. Also if your drivers license isn’t in English you might need to get an IDP or an accredited English translation of your license.
It’s important to know that the rules, for driving in Australia can differ depending on the state or territory where you’ll be driving. So it’s wise to check with the government website or the car rental company before your trip to ensure that you have all the paperwork to drive legally in Australia.