Have you asked AA and been told that it is not possible? Oneworld membership is irrelevant to AA redeeming miles on an airline (it doesn't even guarantee being able to do so -- the BA situation); it is rare for AA to earn but not redeem on a partner airline (though not unprecedented). The AA web site does not break down LAN for redemption, but does for earning, making it ambiguous what is the case -- but does show "single country" awards for Argentina. Wouldn't a LAN flight entirely within Argentina be a LAN Argentina operation? In which case aa.com shows that you can redeem that.