I have worked with a lot of good folks in S. America, in fact I know a team there that is better at text analysis than anybody I know in the states who isn't already busy working for the NSA.
Yes, Mexico is in NAFTA. The agreement needed much public consultation when first proposed, partly because Canadians wanted legal assurances they would be allowed (by the U.S.) to keep their culture, but when Mexico was added it pretty much few under the radar.
I think other nations have been added as a "done deal" without advance public notice.