"Gun deaths" always seems like a silly metric to me. Who cares if you're killed with a gun instead of a knife or baseball bat or whatever else? Why not just compare murder rates?
Guns are an efficient tool for killing people, much more so than knives or baseball bats.
This is, incidentally, the same reason other things that are efficient for killing people and not constitutionally proteced, like dynamite, are not something you can walk in and buy in Walmart.
It's a bit 'noisy' because there are a lot of 3rd world places that are simply quite violent. The US has a lot more than, say, a lot of Europe.
Also, don't discount suicide: guns make that easier too. Some will find a way without, but some would be prevented if it's 'too much effort'.