Several US states will give you a permit to drive a farm vehicle on public roads at 14. Illinois recently passed an amendment to allow farm kids to drive a semi-truck at 16. And there is absolutely no minimum age for driving so long as you are on private land - I have seen 8 year olds driving a pickup truck round a farm...
The mere fact that children as young as 16 can drive on public roads in the US is kind of crazy. On private land no one should give an ass about it, but children in traffic? Crazytalk.