An international driver's license is not required in the US. You can usually rent a car and drive with a valid driver's license from your home country. An international license may be helpful in convincing the car rental agent that you really have a valid license when they cannot recognize or understand your license. Some rental agencies will not rent cars to anyone less than 25 years old. Other agencies will rent to young people but will charge a higher fee. Some agencies will not rent to anyone over 71 years old. Be sure to check on these restrictions if you are in these age categories.
for more information, click this link:
http://www.usatourist.com/english/tips/carrental.html