And that ottbmare, is why we must adapt the Israeli way. You ask a couple of questions of those you "suspect", such as: Where are you going? Why are you going there? Who is traveling with you? etc. And while asking them you look them directly in the eyes and with training you know if they are telling you the truth. It is not rocket science as they say, but it is effective and works. Just ask them.
What I am saying is that virtually every second person of all the thousands upon thousands moving through all those airports every hour would have to be questioned, because half of them look as if they could be from some foreign country, even if they aren’t. Questioning people works at tiny Ben Gurion Airport and at the very limited departure lounges for El Al abroad, because there just aren’t that many passengers and the Israelis have a number of very experienced, astute, intelligent security officials doing the questioning. But for the entire population of passengers going through vast American airports like Atlanta, O’Hare, LaGuardia, Kennedy? You would have to have tens of thousands of highly-trained and highly intelligent TSA employees to stop a large percentage of the travelling public and ask those questions.