Actually, motor vehicles in the US are regulated on a state by state basis. Nothing seems to be universal, including laws. You can make U-Turns in California; you get a ticket for making a U-Turn in Oregon. Oregon has commercial driver's licenses, but if you don't have one and they catch you driving an 80,000 pound truck, you get a warning. In California, I wouldn't be surprised if you'd go to jail. It's like that from state to state all over.