“Or they could just threaten to arrest him and put him in front of a Parliamentary committee. The UK Parliament has that power and they have used it in the past.”
I think that’s exactly what he’s worried about. As long as he stays out of those nations, and keeps enough bought and sold politicians in Washington, he’s safe. He sets foot in any of those countries, he could get served just like that.
Staying out of Canada will be awkward, it’s basically the USA’s hat in terms of location. The other nations? No problem.