As time goes by and this tech improves, restricting guns to a given level will require increasingly invasive regulation. Where once you could accomplish it by regulating manufacturers and dealers and imports, now you have to restrict 3D printers and common items from the hardware store. As 3D printers become common household items, the same level of gun control will require detailed mass surveillance and/or restrictions on common items like pipe and scrap steel.

This may mean that gun control simply fails in non-authoritarian countries, and they either go authoritarian or increasing live without effective controls on guns. As a gun culture the U.S. may be better prepared for this transition.