It seems quite likely there will be some kind of terrorist attack coming from one of the seven ban countries for a number of reasons. Al Qaeda, ISIS, a lone terrorist; they all have a great opportunity to make a strike that would be amplified many times over what it normally would have been. The motivation here is now very high and they would have a chance to affect massive influence over U.S. foreign policy. If they want to provoke far more tensions and less cooperation and trust between the U.S. and the Muslim world, this is a terrific opportunity.
Another threat is the lone wolf that isn't actually a terrorist yet. Imagine a refugee or immigrant that comes over and then watches our news for a few weeks. On a daily basis they've been told people from those countries might be dangerous. All it takes is somebody who can't find a job, perhaps is depressed, doesn't know what to do with their life, is scared, spouse left them, etc. etc. and with this constant barrage of "the bad people are gonna get us" it lends an idea. We saw this with the "war on police" last year. Once the news is jam packed with "group x is at war with the police". Every idiot with a gun that also identifies with group x is then a possible threat. We started seeing people taking shots at the police for fun, out of hate, etc. which was out of the ordinary and started happening all over.
The second phase here after it happens is going to be a political bloodbath. Trump and his supporters will be screaming at the top of their lungs WE TOLD YOU WE TOLD YOU STUPID LIBERALS WE TOLD YOU. This will be almost impossible to counter because of the ultra simplified "we banned them because they're dangerous". "You let them in because you're stupid". "They attacked and killed our citizens because you're stupid". And that will be a wrap.
You could make the argument that this all never would have happened if not for the divisive ban in the first place; but that is far too subtle and involves thinking in non black and white terms and seeing things from an abstract perspective. Perhaps it would have still happened, perhaps not. Even if it is pretty obvious the Trump administration created a problem out of thin air and then called attention to it, the knee-jerk reaction from the terrorist attack will kick all this to the curb as utter nonsense. When people get angry they want simple and aggressive actions, nothing else.
With this political capital Trump will then be able to far more effectively execute his xenophobic agenda and can also use it as cover for whatever else he can hide under its' wings. The long term damage of all this will set back West and Muslim relations years and only add to the heaps of hate, anger, and terrorism. I wouldn't even be surprised if this was the beginning of renewed discussion of a new middle east military campaign.
