"you ess ians"? I am a European and I used that term because the article declared that USA demonstrated such results. For me, USians more clearly distinguishes

"you ess ians"? I am a European and I used that term because the article declared that USA demonstrated such results. For me, USians more clearly distinguishes different types of American. Since I have not read the scientific paper, I was not sure whether, say, Canadians had also displayed similar results. If not, I suspect there is possibly a political / legal / societal cause implied. Amongst other ways, USA is unique in that it is, perhaps more than any other country, populated by people whose ancestors had an ideological reason for living there. It is highly speculative, but it would be really interesting if it could be shown that such an historical filter were somehow behind these results.