U.S. armed violence has a lot more to it than the availability of weapons; statistics are easy to misinterpret as well, since they're really just the proportion of violent crimes that are committed with one particular tool.
Here in Canada, we have higher instance of violence with knives, but unsurprisingly almost the same proportion of violence with guns, despite fairly hefty controls.
The U.S. really just seems to have more violent crime in general than many other countries, and my understanding is that this has been true since well before anyone else had harsh restrictions on the legal ownership and use of firearms.
> I have read some arguments about private protection against excessive government excesses, but I don't really buy it.
The theme of the article is these excesses; if you're not making the connection here, you're never going to make it. Also, incidentally, that's the reason it's in the constitution; I hear that it's an important document over there, but what would I know?
The other good reason for widespread private ownership of firearms is protection against occupation by an invading force, which history has shown to be an unpopular tactic; though perhaps this is not comparable. IIRC the imperial Japanese even stated this as why they weren't interested in occupying U.S. soil.