"...the GAO found that such scanners might not have detected the hidden explosive used by "underwear bomber" Umar Farouk Abdulmutallab...."
Abdulmutallab was deliberately allowed on the flight. A US "intelligence agency" vetoed not allowing him to travel to the US. Don't scan regular American travelers. Find out who vetoed banning Abdulmutallab? Follow that chain right up as high as it will go. That's where you'll find the problem: Plutocrats!