as long as you are flying on a LAN flight number you should be ok, even if on aeromexico metal, since LAN is part of one world.

As per aa.com, Q class intl fares within South America only get 25% of miles and 0.50 EQPs so I believe no different to DL (unless you are trying to qualify through points):
https://www.aa.com/i18n/AAdvantage/p...rlines/lan.jsp