If you are planning to rent a car in the USA, we recommend to bring an international driver's license. This can be obtained at your city's services. It is not mandatory. you can rent a car with your national driver's license, but it is just easier for the rental company or the police if it is an international version, in English.
Beware: In Florida and Georgia it is mandatory to have an international driver's license. There is however some discussion about the legitness of this law, so no action is taken when you do not have an internatonal driver's license.