I wish you luck with your research, but I'm not sure your look at Google Analytics is relevant to this discussion or the Washington Post article that started this thread.
Second, the NSA doc as excerpted in the WashPost article talks only about Google's PREF cookie, which is set only when you go to say Google.com, not when you go to a non-Google property. It's a first-party cookie used for things like saving language preferences when you're not logged in, not for advertising across other properites. (That's what the Doubleclick cookie is for.)
First, as <bdt101> pointed out, you "cannot track a unique visitor across the web using GA cookies" because of the way they're designed: https://news.ycombinator.com/reply?id=6889120&whence=item%3f...
Second, the NSA doc as excerpted in the WashPost article talks only about Google's PREF cookie, which is set only when you go to say Google.com, not when you go to a non-Google property. It's a first-party cookie used for things like saving language preferences when you're not logged in, not for advertising across other properites. (That's what the Doubleclick cookie is for.)