[eindiran]

> registration

If you purchase a firearm from an FFL anywhere in the United States, you are required to fill out an ATF form 4473 and do a NICS background check. There isn't a giant database of all firearms in the US indexed by owner and serial number, but those 4473s do exist and are handed over to the Federal government pretty regularly by FFLs.

> licensing

In most places (eg those with "Constitutional Carry"), the only license you need is to not be a prohibited person (not mentally ill, a felon, no violent misdemeanors involving stalking or domestic violence) and old enough to purchase a gun in the relevant state. But if we just go by raw population, most people in the US would need to go through a more substantial process.

[calvinmorrison]

not to mention you don't need to use a FFL at all in many (most?) cases.

[int_19h]

15 states have mandatory background checks (which in practice means going through FFL) for all firearm purchases.

[calvinmorrison]

15/50... that's not most