An international driving permit is an accepted form of identification in more than 150 countries worldwide. It translates your ID information into ten different languages, so it can be read in many places, even if the local authorities do not speak English.
You'll need an international driving permit to drive in about 80 countries[^1]. But take note—it's _not_ a drivers license, however. You need to have a valid drivers license from your home country with you if you planning to drive overseas. Again, this is primarily about identification and demonstrating that you have a valid driving license somewhere, so you will *not* be taking a driving test to get an IDP.
IDPs are valid for one year and you can choose a future date for it to become effective, up to six months in advance. [AAA is the place to get one](https://mwg.aaa.com/travel/travel-planning/international-drivers-permit-license) (avoid any website that claims to issue IDPs; there are many fraudulent ones). You can just show up to any AAA office, or even mail for one. You'll need two passport photos, a completed application, and $20 per person ($29 if you need the passport-style photos). The prices might be higher for non-members.
Be sure to get your IDP before you leave the country; you cannot use any online services to acquire one as a US citizen.
[^1]: You can search the [US Department of State's website](https://travel.state.gov/content/travel/en/international-travel/International-Travel-Country-Information-Pages.html) for the country you'll be visiting, then find the "travel and transportation" page for an explanation of drivers license rules for that country. Note that for US residents, your state-issued drivers license is valid in Mexico and Canada.