It has worked for guns - the countries where guns are a problem either have very lax regulation, or very lax enforcement (because of a breakdown of government)
Well, there are also countries like Switzerland where there is a substantially higher amount of gun ownership compared to that of the rest of Europe but very few of the same issues of other countries with similar ownership per capita. Though, that’s probably due to the required service training and the screenings that come along with it. And it being a relatively small country.
There are areas of similarly low crime in the US, depending on how you go about drawing lines on your map. Probably it is a mistake to treat any country as a single unit in such an analysis.
I think there are several serious issues with such a claim. However I'll limit myself to pointing out that at absolute minimum you'd need to define "problem" and "working".
For example, I'd observe that organized crime pretty much everywhere in the world possesses weapons. The extent to which they resort to them varies of course, but it seems unreasonable to blindly dismiss that as being due entirely to regulation.
