I agree with you on the mass shootings aspect.
However...
>firearms killings _are_ a pattern, if I recall correctly they are something between 5 and 10 times more frequent in US than other first wold countries.
I personally believe that US citizens are unable to understand how dumb their attitude to weapons is,
You can't compare crime rates without controlling for other differences. Most other first world countries are much more ethnically homogenous than the U.S.
And they don't suffer from the cultural problems caused by the fairly recent institutional persecution of an entire class of people.
It's not very PC to talk about, and I think that the high incidence of crime amongst black Americans is directly caused by the decades of persecution they suffered which causes them to occupy a lower socio-economic position on average than whites, not any inherent racial differences.
But whatever the reason, whites and blacks both have similar access to guns and similar gun ownership rates, yet if you only count white americans, you'll find a fairly similar gun crime rate to the rest of the first World, so clearly, easy access to guns isn't the problem.
The closest country I can think of to our situation is South Africa (Rights recently restored to an historical lower class. Though it's still not a great comparison because of their relatively lower GDP per capital, and different demographics). Their gun violence rate is about 5 times that of the US.