I can tell you why spying internally is necessary. The Boston Marathon bombers, Timothy McVeigh & accomplices, the "Uni-bomber", along with every other 'domestic terrorist' and mass murderer - were American citizens. Also, the president gets informed by the military and U.S. intelligence/police agencies what they are doing without his express consent or usually without his knowledge (until after the factor) and when they (NSA, FBI, CIA, etc.) don't do something you like, BLAME THEIR DIRECTORS - NOT THE PRESIDENT!
And when we hear about some intel operation that netted several terrorists it would seem that we would be grateful, but NO- we want to bitch because it took "SPYING" to gain the proper intelligence, AND THEN - some of us bitch about our privacy, as if we are afraid that the United States government is concerned with our lives when we aren't doing anything wrong.
It reminds me of the Meth Head "tweakers" of my yesteryears who looked for narcotics officers in bushes that were a whole five and 1/2 inches tall and were sure that every police agency ("THEY" that were 'after us all') in the free world was following them because, of course, they had in their possession at least, let's say, a whole quarter gram!
Come on people I know your crazy uncle warned you about that awful "Big Brother" that is coming to get you, but if that is true, he would be locked up! We are just NOT that fu**ing important, OKAY?