I don't think you are making the point you intend to make - the very fact that pulling off a successful attack is inherently difficult is what stops those people, not any security agency.

Same thing with attacks anywhere else. For example: The Times Square bomber couldn't even build a working bomb despite two college degrees and the 2007 London & Glasgow Airport bombers couldn't figure it out either, for their swan song they put propane tanks in their jeep cherokee, lit themselves on fire and drove into a barricade in front of the airport, despite one of them having a doctor's education.

In all of its existence, the TSA has never detained someone who was later convicted on terrorism charges, despite the vast lowering of the standard of evidence for such charges since 9/11. The fact that we've seen so few attacks on "softer" targets (roughly 3 civilians have been killed in islamic-extremist attacks on US soil since 9/11) means that the size of the actual threat is practically zero - including the fools.