Originally Posted by
swingaling
Not exactly. While AA certainly will protect AA-AA and AA-OW, they are not responsible to protect CX-AA. That's because the delaying carrier (CX) is responsible in these situations, not the onward carrier (AA). In this instance, CX would be responsible for protecting the JFK-RDU flight. Whether or not they'd provide any protection is a separate question to which I don't have an answer.
Since AA tells its customers that the late-delivering carrier is
required to protect the passenger, AA is responsible for making sure that the passenger is, in fact, protected. And they do, either by liaising with the late-delivering carrier, or just by re-accommodating the passenger themselves.