When I looked at this sort of thing there was a registration issue as well as the insurance issue. Cars are registered in individual counties in individual states (not in "USA") and you need a local address to register the vehicle. Also the transfer/registration laws vary from state to state, some states requiring a vehicle inspection (MOT) whenever a vehicle changes hands in addition to the routine annual inspections. I think that depending where you are, and like UK, there can be a difference between the registered keeper and the legal owner. So you need to check everything out carefully before you take the plunge.
Forum members living in USA will be able to give a better explanation than mine.