I mean come on, in a country of 300 million people America has 13 000 gun murders a year. 0.00004333 percent. In a country of 30 million Canada has about 100, or 0.00000333 percent, a rate that is 13 times lower. Something's got to be different.
http://www.nationmaster.com/graph/cri_mur_percap-crime-murders-per-capita
Canada has a 0.0149063 per 1000 murder rate, whereas United States has a 0.042802 per 1000 murder rate. That's a difference of 2.87 times. Although Canada still has less murder per capita, we do have our share of murder.. just not with handguns. Mostly, knives. Whether murder is done with guns or knives or whatnot.. I don't think it's really important is it? Murder is murder, and if someone has no access to a handgun, they will likely find something else.
Possible reasons for United States having a worse murder rate:
No free health care system -> lots of mentally unstable people untreated
Warmer climate, temperature. Not only does this lead to irritability, but also gives more opportunity for crime outdoors (e.g., who wants to go out in -40C?)
Far denser population, more over-crowding, and more concentrated poverty (ghettos).
The latter are things Americans have no control over.. and note they are #24 in the world ranking for murder, not bad.
23,677,800 crimes committed in US per year,
2,476,520 crimes committed in Canada per year,
US is about 10x the size of Canada.
I think anyone that wants to lecture the United States on their levels of crime should do a bit of research first. My guess is that it's just the way news is covered in the United States that leads to this 'dangerous' preception the world has.