It's resistance to people who are clearly out of their lane. He is not a medical doctor, yet he's recommending people take it. It's unremarkable that he's incompetent to give this advice, because most people are incompetent to give such advice. I am incompetent to give such advice. What is remarkable is he clearly thinks he's competent to give such advice, and that it's appropriate for him to give it without any qualification whatsoever.
https://mobile.twitter.com/atrupar/status/124655621931107942...
I suspect UK was left off because POTUS has resorts in Ireland and Scotland, and no where in Europe. There's nothing credible about UK being off the list while every surrounding country is on it.