The U.S. is well below the world average in terms of the number of mass public shootings, and the global increase over time has been much bigger than for the United States.
Not only have these attacks been much more common outside the US, the US’s share of these attacks have declined over time. There has been a much bigger increase over time in the number and severity of mass shootings in the rest of the world compared to the US.
Additionally, take a look at the response to the snopes.com “fact check” regarding this research: https://crimeresearch.org/2018/03/fact-checker-snopes-com-big-mistake-comparing-mass-public-shootings-us-europe/