We are an agressive species - it comes of being a territorial, pack-hunting apex predator. But that said, it is still noticeable that US culture is far more tolerant, and indeed encouraging, of violence than any other 'developed' country.

In Europe and the UK, even Australia, you have a mostly unarmed population brought up with ideologies based arounf a steeld social order, collective action and civil conflict resolution via negotiation, litigation or political activism.

In America, an armed population is instilled with an obsolete pioneer/frontier ideology that gives rise to an every-man-for-himself, individualisitc mindset. That mindset encourages and supports direct and violent individual action in puruit of individual aims.

In the UK, if a burglar enters your home and you shoot him dead (yes ,some people here do still have legal firearms), or stab or beat him to death, you will be tried for murder, found guilty and go to prison unless there are extreme circumstances. In the US, if a neighbour enters your house without permission, even if it just to check you're OK, you are legally entitled to shoot him dead.

It is that attitude that makes America the exceptionally violent place it can be from time to time.