Is there is any evidence that any PhD student has ever found it hard to get a US visa because of criticizing the US or US policy?
https://www.thecrimson.com/article/2019/8/27/incoming-freshm...
https://techcrunch.com/2019/09/02/denied-entry-united-states...
(I'm not making excuses for the---dire---state of our immigration policy as a whole. But I was happy to see that this particular case worked out in the end.)