I highly doubt you need to take an RC car to your DMV and get it registered. You almost certainly don't have to do so even for some manned coneyances (bicycles, electric bicycles in a growing number of jurisdictions, vehicles never intended to be used on public roads, etc.).
Trying to compare a toy/hobbyist drone or RC plane to a full-blown car (let alone aircraft) in terms of responsibility and registration requirements is patently absurd.