Canada has 1/10 the population of the US, so one would expect such crimes to happen significantly less frequently. I thinks there's a good point to be made that access to free health care, including mental health care, would result in fewer incidents as well, but it certainly wouldn't resolve the problem, as Canada proves.Why hasn't someone done it yet?
But I honestly don't think it's a cultural issue. I suspect it's a human issue.
http://en.wikipedia.org/wiki/Denis_Lortie
http://en.wikipedia.org/wiki/Mark_Lepine