Yes and no. The US is not the worst country, that is absolutely for sure, but it does have a problem in comparison to other developed countries. And this article only argues that in part, as it attacks the definition of developed countries.
If you look at this graph, you see that the US has the highest gun-related murder rate of all OECD members, by a large margin. You'll get less frightening results by looking at homicide rates in general. The US is still rather far up the list, though.
But I worded my first reply very poorly and apologize for that.