Technically, insurance is not "required in the US", there is no federal requirement, it is required in 49 states.
And there are plenty of other reasons that someone may not be insurable.
And there are plenty of other reasons that someone may not be insurable.
Looks like Alaska provides exemptions too
And technically Virginia doesn't require insurance because you can opt out by paying a $500 fee, but at that point you might as well get some cheap car insurance.
(and beyond this you can 'self insure' in even more states)