For what is worth: if you get AA equivalent to 1k (Exec Plat, OW Emerald) you will have Admirals Club access in SCL and any destination in the US where you arrive (DFW, JFK and MIA) if you are flying in an international ticket (meaning not only within the US)
From OW's site:
Access to more than 650 airport lounges (with one guest) when travelling internationally*, including premium First Class, Business Class and frequent flyer lounges, regardless of the class of service flown that day
*North American itineraries within or between the U.S., Canada, Mexico (except Mexico City), the Bahamas, Bermuda and the Caribbean are not considered international destinations.
From the Admirals Club website:
Qualifying AAdvantageŽ Executive Platinum, Platinum Pro and Platinum
Includes customers on qualifying international flights marketed and operated by American or a oneworldŽ airline (regardless of cabin).
Qualifying international flights
Flights between the U.S. and:
Asia
Australia
Central America
Europe
Mexico City (MEX)
New Zealand
South America
Guest access
1 guest (children over 2 count as a guest)
LA equivalent (Black Signature) gives you:
Access to more than 600 airport lounges (with one guest) when travelling internationally*, including premium First Class, Business Class and frequent flyer lounges, regardless of the class of service flown that day
*North American itineraries within or between the U.S., Canada, Mexico (except Mexico City), the Bahamas, Bermuda and the Caribbean are not considered international destinations.
But from the Admirals Club website:
oneworldŽ EmeraldSM and SapphireSM
Includes customers on all flights marketed and operated by American or a oneworldŽ airline (regardless of cabin).
Guest access
1 guest (children over 2 count as a guest)
Which means being Black Signature would have lounge access in the US when you are flying domestically, which AA's Exec Plat does not offer.
AA has a
status challenge for this cases (see the thread on that in
AA subforum), which involves paying a fee and flying a given number of MQM and EQD during a 3 month period. However, they won't match you to higher level elite status (Plat Pro or Exec Plat), you will have to fly to reach the status.
LA on the other hand, seems to be more erratic on doing
status matches, which means maybe yes or maybe not, but there is one case reported on Statusmatcher in the recent past –note, using social networks– of a match from United 1k to LATAM Black Signature, which gives you more bennefits than lowly Platinum that AA would offer for a match –the only trick appears to be that you have to show them having flown LA in the past 12 months, which I'm guessing you did to get to PMC–.