The problem isn't NSA. It's the President(s) and Congress who define the scope. Call me naive, but I think that most of the folks at NSA, even many of the leaders, are patriots who believe that they are protecting their country.
If you believe that politicians control the bureaucracy rather than the other way around, then I respectfully disagree.
Bureaucrats have expertize, inertia, the ability to sabotage many things, long term stable positions, and care about how things actually are, rather than how they look to the average voter. In many cases, including this one IMO, politicians have the appearance of control, but very little actual latitude in practice.
For better or worse, I'm intimately familiar with the strange working of bureaucracies. Obama's presidency is a textbook example of a politician being consumed by intertia.
That said, politically originated policy turned the FISA Court into a Star Chamber making Supreme Court type decisions, and broadened the scope of NSA's role from spying on the Russians to spying on humanity.
Politicians can curtail those activities as well, either by making explicit policy changes, or by defunding things strategically. It requires courage.
