Your first point may be true, but the US/Norway example is not good evidence for it. There are significant other confounding factors -- relative homogeneity of the population, economic differences, population size, cultural history are just a handful that spring to mind.

Those oft-repeated "factors" can only be factors if you show that they are.

Simply mentioning that there are differences between those two countries does not make any difference you care to list a "factor".

A bit of a broadly brushed analysis. This assumes all other variables/characteristics are equal: economic, social, political, etc.

In that case, maybe there is a link, it's just the other way round...