Every time you send an email to someone in the US they are going to collect it (but not analyze it). Because tomorrow you may send one to Argentina that gets flagged and then they want to look at everything else you've sent, both in and outside the US. And, since I'm now replying to you, they would then want to look at everything I've sent. And they've said they can go one step further and look at everything sent by everyone I've communicated with (3 steps in the US - you, me, my contacts)
If you've contacted a congressman, and they can make up a reason that your contact in Argentina "may be associated with" terrorism, then they can look into your congressman's contacts. When consider everything they want to consider "terrorism" it gets even uglier. A few years ago they tried to label "unauthorized access to a computer system" as terrorism. And wouldn't state that "following a google link to a page that someone didn't authorize you to see" would not be considered "unauthorized access". A court would certainly (I hope) throw it out, but their rules on who is/isn't a terrorist would justify them doing further analysis on you if your contact in Argentina had accessed a computer without authorization (i.e. if they set up a honeypot that "accidentally" got indexed by google and they followed google's link).
It may sound ridiculous and may never happen. But they have the technology and much of the process rules in place to perform pretty detailed analysis of politicians' lives.