Sequence of events:

American Airlines (AA) Brazil website misprices revenue tickets in initial calculation on purchase page. Repricing the same reservation by changing billing country resulted in the correct price, even when reverting to Brazil.

Vast majority of tickets appear to have gone unticketed for ~1 week. It appears that tickets were issued manually, not automatically.

AA states repeatedly and to several outlets that they will unconditionally honor all fares.

AA begins cancelling tickets. Subsequently, they send out cancellation emails implying that the "country of residence" was misrepresented. Of course, this is not the case, as AA never actually asks for the "country of residence" but the billing address which includes the country of the billing address.

Since AA repeatedly and publicly stated that they would unconditionally honor the tickets, even when specifically asked about it, many purchasers relied upon AA's representations and made non-refundable plans. DoT regulations require airlines to reimburse purchasers who relied upon mistake fares to make non-refundable plans. It may be worth writing into the US Department of Transportation (DoT) to complain about AA's handling of the situation and ask for compensation even without having non-refundable reservations, because AA went to great lengths to assure purchasers that tickets would be unconditionally honored.

DoT air travel complaint form: http://airconsumer.dot.gov/escomplaint/ConsumerForm.cfm

DoT air travel complaint mailing address:
Aviation Consumer Protection Division, C-75
U.S. Department of Transportation
1200 New Jersey Ave, S.E.
Washington, D.C. 20590

DoT air travel complain phone line information:
You may call the ACPD 24 hours a day at 202-366-2220 (TTY 202-366-0511) to record your complaint. Calls are returned Monday through Friday, generally between 7:30 am and 5:00 pm Eastern time.

As mentioned by classyflyer and posted by pb9997, if your flight had some kind of legal nexus within Brazil, their consumer protections should apply to your ticket. Here is the contact information for the relevant consumer protection agencies within Brazil. Please be clear in your communication and REMEMBER TO SUBMIT YOUR COMMUNICATIONS IN PORTUGESE.

To translate your communications before submitting them:
http://translate.google.com

www.reclameaqui.com.br
Quote from pb9997: "This site is known to be the most popular, most viewed upon by companies who care about reputation; Though not official, it has proven to be the most respected by consumers and corporations, who may delay answers on their own channels but do take care to have teams focused on answering for this public site. Information written, from both parties, is public."

www.consumidor.gov.br
Quote again from pb9997: "This is the official PROCON site where consumers and companies present their complaints and arguments. It is official, additional care ought to be taken.

I would highly suggest following the order presented; With the first site the company has room to assess impact, prepare an amiable answer and protect their public reputation.

On the second site... well, it's official and what is written by both parties is the basis to act afterwards in a court of law. Ideally the complaint presented should have the Law that explains why a consumer has been impacted and the expected remedy, according [sic] to the Law."

As of 9/8/15 - Individuals who had tickets cancelled in the first round (8/28) have yet to see refunds post to credit cards.

Feel free to update this Wiki with more complete information.