Re: Mozilla are only partly right
There's a minor issue with your stats - you are focused entirely on homicide, except guns deaths are far higher for other things too.
Gun deaths USA 2017 - 19.51 per 100,000. Compared to 0.23 in the UK in 2011 but it doesn't change a lot year to year.
When you look at gun ownership, there is a considerable increase in gun related suicides and accidents too. Sure, people commit suicide in other ways too, but there's nothing so permanent and easy as grabbing a gun... Most other methods take considerably more effort.
---------------------------------------------------------------------------------------------------------------
Looking at firearms related suicides across countries is basically fishing for conflating variables.
Swallowing a bottle of pills (acetaminophen / Tylenol / whatever it's called in Britain will do you in quite reliably; as will sleeping pills or enough vitamin D or enough opiate painkillers), and many of these are sold over the counter in unrestricted quantity in many countries, and exist in most first world houses.
Stepping off a bridge, balcony, or other tall thing is easy, requires no planning, and is both fast and reliable, with a proper site.
Grabbing a high tension line will do it in seconds, or poking on with a metal pole or pipe will also work.
Running a car in a closed garage is classic. So is turning on gas without lighting it.
Or you can hyperventilate, then swim down till you pass out... virtually foolproof, and no proof it was not an accident, for insurance purposes.
Similarly driving into water or a solid object at very high speeds.
Or breathing helium, argon, nitrogen, or a number of other gasses that are not oxygen.
Or stepping in front of a train, subway, streetcar, or big truck on a highway.
Curiously, few people make note of the fact that suicide is believed to be significantly under-reported, and about the least likely to be mistaken for an accident is blowing your own brains out.
Also, guns or not, the US comes in at 34th for suicide rate, trailing such notorious hot spots of gun violence as Belgium, Finland, and Japan. (For those not following the topic closely, Japan has some of the most stringent, draconian gun laws in the world.)
In many cities everyone has easy casual access to suicide opportunities. Restricting guns may cut the number of reported suicides, with a similar increase in 'accidents', or change the method, or a combination of the two. In most cases, method of suicide seem to be driven by social and cultural expectations and norms, not by the presence or absence of guns, while rates are undoubtedly based on a myriad of factors, social, psychological, cultural, economic, etc.