Those stats hide what's truly happening (EDIT: Hide is the wrong word, these stats are deliberately dishonest).
TL;DR: Those stats are listed per capita, and USA is by far the largest country on that list. Statistics have been averaged through 2009-2015 even if listed countries (A lot of them) have only one shooting in the time period. The USA has like a dozen mass shootings in this time period. Multiplie countries are on this list because they had 1 shooting in 6 years and have a population of less than 20million people. It's deeply dishonest.
Norway is at the top due to the 2011 attack that was incredibly deadly. Norway has a population of 5.4 million people today.
All of these statistics are listed as per capita. So because Norway had an incredibly deadly attack and is a small country compared to the USA, it becomes a clear outlier. The site lists norway as having 1.888 deaths per million people, yearly average from 2009 - 2015. Norway has 5.4 million people today. That's about 10 people dying to mass shootings a year. But wait! Remember, in 2011, 77 died total in the event but 67 were victims of a mass shooting. That reaaaaally skews that figure. EDIT: It is also the only shooting that contributes to Norway's Stats in this list.
None of those countries on that list have more than 100 million people today except for the USA (335 million according to wikipedia) (Edit: and Russia, 140 mil). There was a clear choice to massage the data to use per capita to push the message that "the USA isn't that bad" and it's still coming up #11.
This is the reason that other sources don't report these statistics as per capita - they're incredibly rare, even in the USA. 99.9999% of people will not experience them. This doesn't change the fact they are terrible tragedies and completely preventable. You can easily see in other, less biased sources that this is a US problem.
I highlighted Norway because it was especially glaringly deceptive, I expect the other statistics have similar problems.
Further edit: Look at the spreadsheet this data is from (Here's just European countries):
Spreadsheet
THERE IS ONLY ONE MASS SHOOTING EVENT FOR SOME OF THESE COUNTRIES and it's being averaged over a period of 6 years! LOL. LMAO, even. These countries are not having mass shootings every year like the USA is. These stats are so dishonest. Norway has only the 2011 attack!
The US list is longer than the list of all of europe:
US list
This is the source:
Source for bad data