This town is 40mi south of the Canadian border, and you will hear people speaking other languages in public as long as you aren’t in one of the racist bars. Unfortunately, I lived there for a while, and the CBP are constantly waddling into gas stations and shops hoping to relive the glory of making international headlines. (they just arrested someone from the UK, so that strategy must be working)

https://www.independent.co.uk/news/world/americas/montana-us-border-patrol-spanish-women-lawsuit-b1762886.html

All but one of the authors of this paper are dead. I agree with you though, and I would hope a retraction of a paper as serious as this would trigger a review of all the papers connected to the authors.