I think that mathematicians can do the maths...

But it is not just about the numbers, you are probably right that statistically, mathematicians don't have much to fear at the border, but the current administration seems to go out of its way make the US unwelcoming. All countries will protect their borders in some way but they usually don't make a show out of it like the US does.

If you go to a hotel and are greeted by a grumpy guy who asks how how you dare book a room on their property, it is a natural reaction to move to the hotel next door where the staff is hopefully more friendly.