A permit isn't sufficient ... You need an actual driver's license to rent a car in the United States.
Yes, you can rent a car if your age is above 20. You should make your driving license .
It depends of your age. Legislation varies in different countries, but I can say that in every country there is a problem with renting cars if you are less than 21 or even 25. I went to Europe when I was 22 and I rented a car here . This is one of those services that provides a car for young drivers. I think if they call or write a letter, then you can get a clear answer