It doesn't matter if guns are totally banned tomorrow in the USA - there are enough floating about already, to last the crooks, lunatics and fanatics another century. It becomes an evil spiral because nobody wants to be caught out without a gun if they think there's a genuine risk they might be attacked with one.  It's just fortunate for us in Europe that there is the Atlantic to protect us (although there are plenty of Americans with guns at the military bases scattered across Europe).
But just look at Mexico to see how things could end up!
I think the whole gun thing is cultural in the USA.