We'll be flying in from Santiago to EZE via LAN Chile, transiting in EZE and then immediately departing onto the CO flight to IAH. Question, do we need to exit the transit lounge (if there is even one) into Argentina and then check-in with CO and then re-enter through Argentina Customs + Immigration, or can we remain in the in-transit lounge while awaiting our departure to the U.S.? I assume any answer is a bit complicated as the flight from EZE enters the U.S. and I assume there are extra security restrictions which the U.S. TSA imposes on all arriving passengers, so would those additional searches, etc. been already taken care of in Santiago or can they be taken care of in the in-transit lounge prior to actual boarding of the CO flight in EZE.

Appreciate any help.