The 1W carriers that you could use in South America are Lan Chile, Lan Peru, American, BA and Iberia. You need to get route maps for all of the airlines. I have listed the web links for the various airlines about 3 pages back on this 1W site. I have to admit that not all is "Buenos Aires" about the route maps (sorry, EZE is the code of Buenos Aires, a well known joke of the flying community)

Whilst LAN is quite clear in its maps, remember that there is an exception with one of the LAN group airlines, Equador I think but I don't have my magic files with me. BA does fly from Sao Paulo to alternately Buenos Aires and Rio de J. You can certainly ticket on the Sao P to Buenos Aires flight if you wish.

Can someone help me with AA and IB internal south america flights here?

The AA site may be showing some combinations which are codeshares with LAN or they may be doing it themselves. Let's see what the south america specialists have to say.

DNW, Viajero where are you..