This has been discussed in forums around here several times. My understanding is that if you book 2 oneworld flights on separate tickets with a legal connection and things go sour the first carrier has to accommodate.... but do your own research. In any case I wouldn't rely on that... An AA representative in SCL helping you with LAN? On a route served only once per day (or so)? I wouldn't be surprised the whole thing turns into a huge mess... unless someone here has had a positive experience in a similar case.