Oh no, you are on a list of 3D printer owners. Oh no, the world will end.
And when they ban manufacturing of guns, first people they're getting search warrants for are those with registered 3d printers. Why else have the list?
And registering your purchase is like such a common thing, you do it’s when buying ammo, a firearm, a car, an apartment…
Most US states don't require registration of either firearms or ammo. Background checks are only required for the firearm, which does leave a trail, but only of X serial number was purchased by Y person on Z date. If you make your own firearms, depending on the state, serial numbers are optional, or can be whatever you want.
Also my car is only registered if I want to drive on public road ways. Not on purchase. Apartments, houses, etc, only apply when I want to update my license to drive, or vote. Otherwise the government couldn't give 2 shits.
You live in a horrible surveillance state and defend it. Most modern countries are to some degree, but you'll gladly hand over you internet, contact and travel history when asked it seems. All for the benefit of something that doesn't care about you.
Finnish neo-Nazis used 3D printer to make guns in preparation for ‘race war’ (www.theguardian.com)