Vehicle registration is handled by the US states, not the national government.
Some US states require proof of insurance as a pre-requisite for vehicle registration.
visitor.us registers all of its customers’ vehicles in Montana, which does not require proof of insurance in order to register a vehicle.
Liability insurance is required to drive a vehicle on public roads in the United States, and it’s your responsibility to maintain insurance on your vehicle, so make sure you have an insurance policy in place before you hit the road.