Some great points in your post, DMP, and thanks .. I agree with a great deal of it. But, I've singled out the point which I think I should disagree with.
What I think you're reflecting, without knowing it, is the great psychological differences involved. Most of us don't own guns because we've never considered it, because guns just aren't 'out there' for us to consider buying. But more, our society would consider carrying guns almost to be an alien concept. I'm far from young, but I've lived my life never once encountering anyone, ever, from the UK who owned one.
The one time I did find someone who owned a gun, as it happens, lived in Germany, and the only reason he had his gun was as a WWII souvenir, from his Third Reich army days. Otherwise I've literally (knowingly) never met a gun owner in my life.
'Trusting ourselves with gun ownership' isn't a factor. They're just not a part of our lives.
The British get reports of shootings in America, maybe a shootout at a school, or whatever, and I think the reaction is one of a lack of comprehension of why the gun was freely available enough to the shooter in the first place. But more, the overall reaction would be that America earns those situations just because guns are available. Putting it bluntly, they struggle to see it as a mark of a civilised country, that such freedoms to own firearms can exist.
We have NO enshrined right to carry guns, as you have (the very concept doesn't exist here). We have no Constitution that governs such freedoms at all.
And that is the big difference. Many generations of Socialist influence ensure that any move towards even considering gun ownership here will never happen. Those who preached otherwise, in the UK, would be thought of as 'gun nuts', needing professional help ... .