With the two big conferences looming this year, the APS March and April Meetings, it will be interesting to hear how the recent presidential executive order banning entry by visitors from 7 predominantly-Muslim countries will have affect. Citizens from countries such as Iran already had a long and arduous process in gaining a visitor visa to come to the US, so much so that many won't even bother to try.
So now, with the entry ban, looks like this will have an impact on visiting scientists from these affected countries. Unfortunately, this will create an even bigger ramification, because international organizations will be less inclined to hold major conferences in the US where some of its members will not be allowed to attend. This should have both scientific and economic impacts.
So far, there has been no official word from the APS on this matter.