Yes, it's a growing problem in North America. The problem is not the objects themselves, but their regulation, given that they leave no traces. For the time being, Canadian and American legislation identifies firearms on the basis of the stock. The serial number is printed on the stock. As it's possible to print or make these parts, it's possible to circumvent the legislation. The solution might be to identify all components of a firearm, whether a handgun, a rifle or anything else. The definition of what constitutes a firearm should thus be expanded and perhaps include the barrel, the breech and other components unique to firearms. That, to some extent, is what's being done in Germany.
It is of course difficult to prevent everything, but it would reduce their proliferation and, most importantly, make the importation of Polymer 80 products completely illegal. These are weapons that are not complete. Under American law, they are not considered firearms, but rather scale models. They are legal in the United States. They can therefore be carried and made there. They seem to be very popular here among people who want to obtain unmarked guns.