That's along the lines of if something happens to one person it is a tragedy but if it happens to a lot of people it is statistics.
The numbers are now high enough that it has become a statistic, and one worth noticing. It also draws attention because the list of 7 countries could easily be expanded (on a twitter inspired whim no less).
It's the capriciousness and the uncertainty coupled with the numbers that make it an item, not because it is Trump or someone else at the helm, if Obama would have done this it would have resulted in much the same level of pushback.