I know this is something that needs far more research than what I could expect someone on a Q&A to provide, or could even be conveyed on a Q&A website. But we have an awful lot of people living on public assistance in the States. And dare I say, fewer in Canada ON public assistance than in the U.S. and a lower percentile of citizens on public assistance in Canada.
So is the absence of social welfare programs and a safety net really it?
I lived on S.S. disability for three years and could have stayed on longer, and still have Medicare and Medicaid (Tenncare).
The reality of far fewer below the poverty line certainly makes sense, but Appalachia and N Alabama and the Ozarks also has a huge percentile of people living in poverty. with les crime (though still considerably more than Canada) But, as Seawulf points out, they also have lower population density.
The Netherlands has a relatively high population density, however. It varies from city to city but many cities in Europe and Asia have low crime but high density, and less crime than the U.S.