About the chemicals shakran, I do not know enough about the matter specifically so I would say "maybe". Obviously mercury and other toxic stuff that people put into their systems can't be good, but do they make one violent, and not depressed or ill or tired or obese? I know that some people put a lot into it, that ingested chemicals in our food, water, plants etc are responsible for much of the criminal behavior in America. I don't know.
But watching for myself the behavior of young human children, right out of the womb before anything has had a chance to leave its mark, tells me something is up on a very basic, fundamental level. Further reading into child psychology has reinforced what I've observed. A baby with its new little teeth will bite your finger and laugh...what does that say? And its not only humans...take birds for example. Young birds commonly kill off their weaker siblings and toss their bodies out of the nest. Lions are obviously extremely territorial; they'll simply kill any outside lions who enter a certain space. Fish...another extremely territorial animal that will defend its eggs and territory to the death. Ants are the Genghis Khans of the animal world - they form huge armies and wipe out anything in their path. Maybe its competition over scarcity of resources?
mixedmedia...all I will say about America as somehow intrinsically more violent than the rest of the world:
look at the numbers. America has a lot of crime, because it has a huge population, a lot of inner cities (we have many, many more big cities than most other nations) and poverty. But per capita, there are many countries more violent than America. New Zealand, Denmark, Finland, Columbia, even Britain has a higher rate of crime than does America.
But I am curious: what do you think is going on here that is unique to America?