Due to "security concerns" the NSA operates relatively autonomously, and, by design, even the president and courts have limited oversight.
This isn't true at all The President has ultimate authority over the actions of the intelligence agencies. The Congress has ultimate control of funding for the intelligence agencies. Further, both houses of Congress have intelligence oversight committees that were formed in the wake of multiple scandals from the 1960s and 1970s.
None of this is new. FISA was written as a direct result of the US Army spying on domestic protests by American citizens. The domestic and overbroad spying by the NSA is exactly the type of thing that FISA was originally intended to halt.
Every time we pass a law to stop some shitty corporate or military behavior, it gets slowly watered down over the years until it's incapable of meeting its original goals.
While all technically true, the problem happens when these agencies straight up lie to Congress or the president about their activities.
James Clapper, the Bay of Pigs, etc etc. If you believe those oversight committees are worth anything, well...