You're all over this thread with the same point: what makes you think that not letting new cases in (in this case, travel from hotspots) is somehow not improving the situation?

>the math is very simple

Yes it is. There are infected people in Europe. Stopping travel from Europe = less infected people in the US. Yes, there are already infected people in the US, but a travel ban will neither increase or reduce that number; it's irrelevant.