Earlier quoted context omitted.
The framing of this comparison is fraught due to unequal bucketing. Most other countries are the size of US states or even cities, so they can boast individually low numbers while in the US everything gets bundled together. The US should instead be compared to something like all of Europe or all of Western Europe.
Perhaps, a comparison versus the rest of the G7? https://www.cnn.com/2018/05/21/us/school-shooting-us-versus-...
We do absolutely have higher rates of targeted gang violence than other countries, which after controlling for factors like density and poverty is highly correlated to young urban male demographics that aren't as prevalent in other developed nations. There is no single policy that can solve the numerous social and systemic failures that generate this problem, but due to the nature of these vendettas they would assuredly be carried out with knives and shanks in the absence of guns.