I couldn't find an official page which addresses the weight of vehicle and foreign licenses, so I head to truck campers renting agencies, and I found the answer there.
With a normal driving licence you are allowed to drive every recreational vehicle. It doesn't matter if it's a small motorhome or a large buscamper. The U.S. has an agreement with most countries whereby the renter's full national driving license may be used for a period of up to one year in the U.S.A. International Driving Permits are generally not required in the U.S.A but it is recommended to carry one. If they are taken, they are only valid in conjunction with a full national driving license.
and from moturis.com:
Drivers License A national automobile driver's license is required. We recommend customers
to carry a translation of the national driver's license or an international driver's license, but
under any circumstances, customer must provide a valid national driver's license at pick-up.
Minimum age is 21 years for all vehicles
From that I understand that any driver's license is welcomed as long as you are 21 and the license is in English or you carry an international license along with it.