It'll be very effective at this. Most people aren't going to establish a plausible social media profile after they figure out they're going to the US to live/work/whatever.
"Real" spies and terrorists and whatever can obviously afford to setup enough cover. (Though there is the case of a spy getting discovered because she used her real frequent flier number while traveling under aliases.)
At best, this might put a chilling effect on Facebook and other things like that, which is probably a net win for humanity.