Compare the USA situation to countries at war or with armed insurgencies and, of course, it might seem even tame. If you aspire only to give your citizens the security of a corrupt developing world dictatorship then this comparison is probably useful.
I read the parent comment again and I don't see the phrase "at all" in there, so the clear implication (at least to me) is that they meant mass murders by gun happen far less often.
Next, I'm assuming that by "mass shootings" you mean the FPS, Single Player category on there (since the only other FPS aka shootings category is Co-op Mode which seems to be almost exclusively terrorism and gangs, not "common people").
Here is the raw data: https://pastebin.com/rfHy5KUu
Here is the aggregate by country: https://pastebin.com/NPi3kELY
USA has 'only' 4.3% of global population but 17 out of 50 top ED loner shootings and one third of deaths and almost half of injuries.
If that's not a phenomenon then I guess nothing is.
Perhaps I should just publish some results. Seriously, every time I debate a data scientist I just send them to the data. Heat correlates more with mass murder than anything... Like I don't really get it.
While of course no country can ever be mass shootings free and immune to them since a determined person (ISIS, Breivik, etc.) can always get a gun eventually I was just pointing out that based on the cited stats USA is standing out with regards to frequency (even compared to much more populous China, India, EU+UK+Norway, etc.) so there is some US specific phenomenon related to mass shootings (for whatever reason, gun availability, society, heat, magic, that's beside the point I was making).
Sorry, but this is completely false.
I am not going to link to it for reasons of taste, but you can google "encyclopedia dramatica high score" for a very thorough run down on mass shootings. They occur globally and are by no means a phenomenon isolated to the US.