If I was the director of an agency of the size of the NSA and was evaluating the options purely from that perspective, I'd aim at creating a file on every living citizen on earth, including their social network topology and their activities. Basically a Google search engine that includes information not publicly accessible. I'd create much larger files for persons of interest and authorize targeted surveillance of them, of course, but with today's means to collect data a complete world database on every living and many dead persons is well within the technical capabilities. It also makes sense and is rational, if you put aside moral considerations.

That's how I evaluate these things. If it makes sense and can be useful, it's likely going to be done. Notice that there is no law against this in the US if you exclude US citizens. It's perfectly legal and within their mission parameters to do it for non-US citizens. I used to think my judgments were a bit too much on the paranoid side but when Snowden published his leaks it turned out that I was roughly right about every capability the NSA had except for their internal security.