Have the terrorists exposed America's Achilles heel?

Ever since the incidents of 9/11, the US has been on a warpath in the domestic front--with security.  Looking back, it now seems like the disgusting coinage of "homeland security" was nothing trivial.  It has evolved into an uncontrollable police state, writes Megan McArdle:

It seems to me that the TSA ratchets up the security the way a government in a police state would.  Perhaps there are some public deliberations that I'm missing, but from the perspective of a passenger, there's no attempt to achieve balance.  There's simply a progressive ratcheting of our liberty ever downward.  Did Richard Reid try to put explosives in his shoes?  Then we must have our shoes scanned--even infant shoes too small to blow anything up.  Did someone else attempt to set his underwear on fire?  Well, if you can't strip them down to their skivvies for a check, do the next best thing:  find a machine that does it virtually.

Somehow, this seems like a questionable reaction to two attacks that failed.  Especially since they failed for the same reason that any similar attack is likely to fail:  the amount of explosives you can smuggle in your underwear or shoes is necessarily small, meaning that you need to be in the cabin to detonate them if you want to be sure that you'll bring the plane down.  And it's really hard to set your underwear, or your shoes, on fire without your fellow passengers noticing.  In Asia, I've never been required to have my shoes scanned--not even to get on a US bound flight.  And yet, we have not been confronted with a rash of exploding planes out of Taipei or Saigon.

The TSA seems to have assumed that the ratchet could keep moving downward indefinitely (notice that they never seem to find ways to make searches less invasive and annoying.)  I think that the backscatter/invasive search deployment may finally have gone too far--although I freely admit that this may be wishful thinking.

Yes, it is wishful thinking.  Because, as in police states, we the people comply without protest.

Have the TSA screenings ever resulted in would-be terrorists being apprehended?

Citing national-security concerns, the TSA will not point to any specific cases in which a screener stopped a would-be terrorist at a checkpoint. Nonaffiliated security experts, such as Bruce Schneier (who coined the term "security theater") argue that that's because this has never happened.

Anything else on the efficacy of the TSA?

What's more, the GAO noted that at least 16 individuals later accused of involvement in terrorist plots flew 23 different times through U.S. airports since 2004, but TSA behavior-detection officers didn't sniff out any of them.
What these numbers don't get at is whether the TSA airport screeners prevent terrorist attacks through their very existence—deterring plots by hanging around. This is quite probably the case, but it's not obvious that they prevent any more attacks than the private contractors who handled checkpoints before the Aviation and Transportation Security Act of 2001 went into effect.