I guess it's not back to the topic,

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You can misuse numbers if you take them out of context. How and why are children killed? What are the populations of the nations quoted? How do those numbers factor as a percentage of population? Are there cultural differences? Criminal economic factors? I would say that a large part of the children killed are due to gang activity, which is primarily a U.S. cultural problem. I follow several papers on the West coast, Sacramento Bee, San Jose Mercury News, Contra Costa Times, San Francisco Chronicle. Most of the gun killings are gang related, from your blood and crip affiliated gangs to Hell's Angels and Mongrols motorcycle gangs. Now you're starting to see sub groups within the crips and bloods doing their own gang thing selling drugs and running prostitution. A lot of the killing is protecting their business and eliminating witnesses that have talked although sometimes just ego, getting payback for being slighted. Some of the worst is in Oakland and Richmond, California. That's just NorCal, for a real look check out L.A.. Recently down in Compton for my wife's family reunion we were rolling down the street next to a low rider with a custom metallic blue paint job with their car club plaque in the back representing their particular gang which was a sub group of the crips. A couple of real thugs right there openly on the street.
Gang turf map for L.A.:
http://www.streetgangs.com/maps/southla_turf.html
To see how the U.S. is unique, just look at Mexico right now with the drug cartels waring with each other and even attacking the police and government. There are criminal economics involved there because Mexico is used to run drugs into the U.S. even utilizing underground tunnels. The numbers of dead in towns that border the U.S. lately is staggering. There have even been high ranking law enforcement officers that have been assassinated. One group threw grenades into a crowd during a celebration.
All that to say, in and of themselves guns are just tools. If you're properly trained to handle, use and secure them, they are not a danger to anyone but would be criminals. Even with more common tools people are killed because they just aren't safe with them. Look at the push to change the safety mechanism on nail guns after so many accidental deaths. I've used nail guns myself, and I treated them as something just as dangerous as a real gun. Whatever the tool, you the owner and operator are responsible for its safe operation and to secure it around children.
With training and skill I could be just about as deadly with a Samurai sword as with a gun. In these other countries, how many are killed with blunt objects or knives? Because of strict gun laws, different cultural problems, criminal economics, you probably just see the deaths shift to alternative methods. Where there is a will, there is a way. Guns in and of themselves are not the problem.
Bugz