The rule for a US licence
Czech authorities require non-EU license holders to carry an IDP with their national license. As elsewhere in central Europe, the IDP functions as the accepted translation of your US license.
Prague is a common starting point for road trips into Austria, Germany, and Poland, and requirements differ across those borders, so check each country on your route rather than assuming one rule covers the trip.
Live in Czech Republic, or hold an EU/EEA licence?
A licence issued in Czech Republic is what you drive on at home - an IDP is a translation of a foreign licence, so it does not apply to you here. An EU or EEA licence from another member state is also valid in Czech Republic on its own, under EU Directive 2006/126/EC. In neither case do you need an IDP.
At the rental counter
Rental agencies in Prague frequently ask US customers for an IDP at pickup.
What the permit covers
An International Driving Permit is a translation of your licence into a standard multilingual booklet, issued under the 1949 and 1968 road traffic conventions. It is not a licence, and it is never valid on its own: you carry it with your own licence, and police expect to see both.
It is issued against the vehicle classes already on your home licence, and it never adds one. If your licence does not cover motorcycles, an IDP does not let you ride a scooter in the Czech Republic; if it does not cover a heavier vehicle, the permit will not cover a camper or a minibus either. The permit restates what you already hold, in a form the local authorities can read.
Driving in more than one country?
Check every destination on your trip at once - Czech Republic is already filled in.
Check your tripOther destinations
Informational only, not legal advice. Requirements change and vary by length of stay, rental company, and vehicle class. Always confirm with the destination's embassy or your automobile association before you drive.