Even if you buy the ticket from American,
legally it doesn't have to do anything.
Congress leaves you at the mercy of the airline's unilaterally-imposed 'conditions of carriage' which you had to accept by "adhesion" (you cannot negotiate your contract) when you forked over your hard-earned money. In AA's case, they
state:
American will endeavor to carry you and your baggage with reasonable dispatch, but times shown in timetables or elsewhere are not guaranteed and form no part of this contract. American may, without notice, substitute alternate carriers or aircraft and, if necessary, may alter or omit stopping places shown on the ticket. Schedules are subject to change without notice. American is not responsible for or liable for failure to make connections, or to operate any flight according to schedule, or for a change to the schedule of any flight. Under no circumstances shall American be liable for any special, incidental or consequential damages arising from the foregoing.
Their obligations are pretty clear, even though in practice, as spelled in this thread, they do more -- whether you buy their ticket from them or not (international travel is governed by IATA Passenger Services Conference Resolution 735d "INVOLUNTARY CHANGE OF CARRIER, ROUTING, CLASS OR TYPE OF FARE".
If you don't like what you're legally entitled to (and you shouldn't!), please take your time to
write your Congressperson: there's been a push to try to get US citizens some legal protection (see
www.flyersrights.org/billofrights.html), and this effort would benefit GREATLY from additional direct voter pressure.