I agree with what you say. There are cultures where most of the men routinely walk around with a gun tucked into their waistbands. And, yet, shootings are rare.
I lived in several poor countries where men walked into the bank with big machetes and knives on their belts and nobody blinked an eye. Because, although every man woman and child in the country knew how to use knives and machetes, it was unthinkable that someone would use a weapon like that on a person. (Until a civil war breaks out-- then all bets are off.) So the presence of weapons does not have to mean people use them on each other, as the Iceland case shows.
In some cultures people try to de-escalate conflict before it gets violent.
In the US we have a combination of lots of weapons around, coupled with the tendency to actually use them
, and to have them loaded, easily available and ready for use. We have a culture that, historically and psychologically, seems to think that violence is a good way to solve all kinds of problems.
In the US, I can't tell you how many times in an argument I have heard one or both of the combatants threaten to "go home and get my gun". Guns are brought up whether there is a car accident, some moms whose kids cursed at each other, a fight between teen girls over a boy or a dispute among grad students over an unfair grade from a professor.
That need to bring a violent "Dirty Harry" resolution to any conflict is a bigger problem than the guns. But guns add the horrible element of instant, even accidental death from a distance, where fists, sticks, and even machetes and knives don't.