As Larry Correia noted on the Book of Face:
"[T]o keep terrorists from getting onto a plane with a bunch of sitting ducks, you added the TSA bottleneck, where now you have a giant group of sitting ducks packed into a different, even more easily reached place. Duh....and if they move screening back to the airport access road, they set off a truck bomb in the traffic jam rather than a backpack bomb in the terminal.
So instead of blowing up the passengers on one flight, they can instead blow up the passengers waiting for twenty flights at the same time. Brussels and Istanbul proved it worked, so it will be coming soon to an airport near you."
The reductio ad absurdum of this, of course, is to avoid creating the security bottlenecks that make such target-rich environments by putting a TSA checkpoint outside every front door in America.
There's just no practical way to nerf the world.