While it's a different situation, it's still not a good one. The lack of rights for foreigners, the NSAs reach, the willingness to prosecute citizens of other countries, long detentions and harsh penalties for computer crimes etc. puts people in a situation where the US government can make things very uncomfortable for them. I do think some risks with e.g. mass surveillance have been exaggerated, like being pursued on a basis of keywords. But if the US government actually has evidence against you of things they consider illegal, your legal protection against abuse will have weakened. So while it's unlikely that the FBI has a list of dissidents that they've correlated with collected evidence and are just waiting for people to cross the border, it's still not a situation people should have to, or have to, accept.