The NSA is the modern day praetorian guard that controls the levers of government and sells the vacant seat of the emperor to the highest bidder.
In case you don't know what I'm talking about, the Praetorian Guard was the Roman Emperor's own private guard, sort of like the secret service. Except that with time 'mission creep' happened and before you know it the Praetorian Guard was killing the emperor and selling the seat to the highest bidder; and future emperors learned who to keep happy to keep power.
The Praetorian Guard leaders were often the second in command in the Roman Empire and essentially ran foreign affairs through consent of the emperor.
It took until this guy named Diocletian to finally get his arms around these guys, reduce the their power and size, and banish them to a small camp outside the city limits and not much was heard from them again.
And not too long after, an emperor named Constantine moved the empire from Rome to Istanbul, I mean Constantinople, and the Praetorian Guard was history. Of note, those eastern emperors eventually hired their own private guards -the Varangian Guard - consisting of viking and anglo-saxon warlords because they had a reputation of being loyal but ruthless protectors.