Spying on terrorists is hard so the NSA spies on Americans instead

One thing I don’t think anyone has mentioned yet about the current NSA scandals is how easy it must be for the NSA to spy on Americans compared to our enemies.  I imagine that’s why the they does it.

Terrorist groups are secretive, private and rarely speak English.  Americans are culturally extroverted, have both burning (and boring) secrets equally matched with a fervent desire to express them without being judged negatively, and speak passable English in most cases.

If you were being judged on the number of “Possible” catastrophes averted, who would you rather spy on?