What if some patent troll learns I'm going for a visit to the US? What if they secretly tell the police to arrest me at the airport and then sue me over some dumb patents?
What if somebody makes a joke on the Internet and then I'm detained at the airport and interrogated whether I have fought in the Ukraine?
What if they learn I have some Muslim friends and decide to question me if I knew of any bombing plans? What if they send me to one of their secret prisons to beat out my consent to spy on my friends?
You see my problem?