> If someone doesn't have a government ID, the state probably doesn't even have current contact information for them, know whether they're a resident or not, or perhaps even know they exist.

That's why I was saying like the census. The idea is cover all individuals by canvassing all the places they could reasonably be living. All the collective levels of government certainly have near-complete records of that.

Don't some US organisms like the IRS or Social Security know everybody living in the US?