"U.S. citizens are permitted to drive in Ireland for the duration of a visit up to 12 months as a tourist. If you wish to apply for an International Permit for use during your visit you can apply through the AAA in the U.S. – you can find more information here ."
https://ie.usembassy.gov/driving-in-ireland/
EDIT:
To clarify the above, Ireland does not require US or Canadian (generally speaking, licenses issued in English) license holders to get an IDP.
"Conclusion
In conclusion, for most foreign visitors, an international driving license is not required to drive in Ireland.
National driving licenses are generally accepted, but a certified translation or international driving license is recommended if your national license is not in English, or if you come from outside the EU. By following these simple tips, you can make the most of your exploration of Ireland’s roads, legally and safely."
https://www.go-to-ireland.com/travel-organization/do-i-need-an-international-driving-permit-to-drive-in-ireland/