From wikipedia:
https://en.wikipedia.org/wiki/Mass_shootings_in_the_United_S...
> The United States has had more mass shootings than any other country.
https://en.wikipedia.org/wiki/Mass_shootings_in_the_United_S...
> The United States has had more mass shootings than any other country.
If you'll check the references for that statement, they're all news articles based on a single study.
A study that the link above already discussed. A study that "excluded gang-related shootings, drive-by shootings, hostage-taking incidents, robberies and acts of genocide or terrorism."[1]
In other words, it's a custom-designed, cherry-picked statistic designed to make the US look worse than it is.
1: https://www.washingtonpost.com/politics/2018/09/05/does-us-l...
And I've never understood who decides whether a mass killing is an "act of terrorism" or not.