They aren't really an issue anywhere because if someone really wants a legit gun they are not that hard to buy on the blackmarket or even produce yourself. There just isn't much actual demand for 3d printed guns, people do it because its fun and an engineering challenge. If someone can buy a tabletop mill or lathe, or if they are patient with a file, we have 100+ years of well documented and engineered gun designs anyone can copy. Like you are seriously only cutting a couple hundred bucks off the price between buying a 3d printer or a CNC mill and all the CAD files you need for either version are easily accessible online.
Yeah, and while 3D printing a gun is cool and all, you can’t print bullets, so the person who is interested in printing guns is at the intersection of two hobbies: 3D printing and gun ownership. It’s a niche.
Everybody else who needs a gun for lawful purposes (i.e. self defense) is simply going to purchase one from a reputable manufacturer.