The intelligence agencies in the United States are the best in the world.
Mossad would disagree with you.
Ever wondered why no one hijacks El Al flights?
I always thought it was due to two factors:
1) Proper security design at the airports that make all the obvious single-person
low-tech attacks fairly unlikely to work, forcing the use of high-tech or
2) The reluctance of anybody to be the on-the-ground part of a conspiracy or
the seller of a high-tech solution, when you *know* that your continued life
expectancy is very short unless you plan to spend the rest of your life hiding
under a bush in one of the more inhospitable jungles of New Guinea.