@SW-User Most of the homicides involving a firearm and committed by criminals shooting at one another. Those criminals are going to have firearms whether they are illegal to own or not. Is a mass shooting a situation where a criminal shoots a number of others, killing others being the sole reason, or is it when a bunch of gangbangers or bikers have a brawl that ends in a gunfight? Thise numbers are included in the stats for mass shootings. Depending on who is tracking it is usually 3 or 4 victims excluding the shooter. Some only consider deaths while some also include wounded. There are virtually no accurate numbers from any source because there isn't really a definition of a mass shooting.
How do the levels of gun violence compare in Ireland and the US?
In Ireland, there were 17 homicides by firearm in 2014. (More recent data shows that there were 39 homicide offenses and 2,517 weapons and explosives offenses in 2021.
Switzerland has very few homicides, almost no firearm related crimes, yet children are encouraged to learn to shoot, there is an annual shooting match for children. They have a very high rate of civilian gun ownership as well, not quite as high as the US but significant.
Different levels of crime, different cultures, there is more to the crime in the US than just gun ownership.