Seing the bar as a response to a terrist threat doesn't make much sense. There have been no terrorist incidents in the US involving anyone from the countries Trump picked to put the bar on. The 911 terrorists were almost all from Saudi Arabia.

Today there is a story about a young teacher from Wales accompanying a school party to the USA, who yesterday was pulled off an airliner on its way to the States, by US Security., at Reykjavik. No connection with any of the places Trump had tried to bar, but his family was from Bangla Desh, and he is Muslim, which was evidently enough.