I think that's probably unlikely. It's a fare that's filed on LA/JJ only (plus some other non-OneWorld carriers like Avianca and Aeromexico). AA does not have the fare filed. You might be able to force AA.com to price it but I was not ever able to get that to work.
Edited to add this:
Some of these fares ARE AA-filed (like LPB and VVI), so those you can obviously book anywhere you would like including AA.com. The fares I referenced above for Argentina require booking via Orbitz or Expedia to get the routing options via JFK or other cities, as they are JJ/LA-filed and LAN and TAM websites do not show widespread routing options. I also saw some very limited options for LAN-coded but AA-operated EZE-DFW-LAX, which is the new AA 787 route. It was substantially more expensive (about an extra $800), but if that's worth it for you to get the AA 787 it's available. You will have hunt for it though.
Thanks for the detailed explanation. I booked via SCL and am looking forward to spending a full day there on my way to AEP. The return is via LIM on a LAN 787. I think I will stick to this schedule without any alterations with this new information.