The Corporation for Public Broadcasting, PBS, and NPR broadcast propaganda for US political parties (one, but the other one gets it too, in profiles of industrialists, shows promoting various industries, especially Pharma). I have close friends and colleagues in most of the countries you identify as "strong democracies." They just don't have the culture of violence that US has. A very interesting article, and great coverage of history - but I'm not sure the conclusions are warranted.