This is factually incorrect.
Almost every country in Europe and most other industrialized (and non-totalitarian) countries around the world have much lower gun ownership and (partially consequently) lower murder rates than the USA, despite in many cases having a considerably higher general violent crime rate. Thus, demonstrably having "made a difference." Does not prevent "gun violence," but does significantly reduce it.
It is true that in UK only criminals have guns, but even most of them do not have guns, thus violent attacks are less likely to end in death.
I strongly support the 2nd Amendment, but I think it is dishonest to try to claim that there aren't highly unpleasant side effects to the 200M guns floating around America.
On I believe the same day as the Newtown shooting, a nut in China similarly attacked schoolchildren, except he didn't have a gun. So he used a knife.
23 people were injured, but there were no deaths. So far, anyway.
The problem here is that guns indeed do not kill people, but they make it so much easier and more efficient. Does anyone seriously contend Lanza would have been able to kill so many children armed with a knife? Or that the nut in China would not have been more deadly armed with a gun?
One of the costs of an armed populace, unfortunately, is that occasionally one of those armed citizens will go off the rails and do something like this.
This cost is vastly outweighed by the benefits of an armed people, but I think it is dishonest to claim the costs don't exist.
You need to look at the total homicide rates from before and after gun control was put in place. It does not matter to the person murdered if their murderer uses a gun or a petrol bomb. If you look at comparable populations in countries where guns are common, the murder rates are about the same. Murder is a cultural phenomena, which has little to do with the weapons used.
As an example, people of Japanese descent (when we kept such figures) in the United States, where guns are plentiful and easily available, had murder rates slightly lower than Japanese in Japan.
I would question your assertion that other western nations have much lower gun ownership than the US per capita. Canada, Japan, Switzerland to name a few.
Also you print the myth that the British dont have guns. True, most British dont own guns, and contrary to NRA type myth, never have. But we in the UK can legally own a rifle or shotgun, most handguns are banned except in NI where they are legal. And many thousands do own weapons. I myself own a rifle and shotgun.
Apologies for being boorishly pedantic after that compliment, but I can't resist pointing out that your statement 'it is true that in the UK only criminals have guns' (often repeated here) is incorrect. There are many thousands of legally owned guns, since the types of guns which were always the most widely-owned in Britain (shotguns and sporting rifles) have never been banned. It would, however, be true to say that most handguns in circulation are criminally owned.