Countries that Require Americans to Obtain an IDP to Drive Overseas
International Driving Permits are Required* in the following countries for US Licensed Drivers: Australia, Austria, Bulgaria, the Czech Republic, Estonia, Italy, Japan, Poland, Romania, Serbia, Slovenia, Slovakia, Spain, and Thailand.

In Hungary, US-licensed drivers are required to possess a certified Hungarian translation of their domestic license.
Learn More: https://www.autoeurope.com/international-driving-permit-faq/?c=144931