EZE - ATL screening
 

I've seen reports of secondary screening for USA flights, is that literally "at the gate" or a queue (gauntlet) to pass in order to proceed to the gate area. If latter, is there D1/Elite priority for that?

Unless something's changed, EZE had the standard secondary screening where anyone who has the SSSS on their boarding pass got an additional check before boarding. No separate, gate-specific screening area otherwise - standard, open-to-the-concourse gate like anywhere else.

There will be tables set up where everyone gets at least a cursory inspection during the boarding process. The only "priority" is that it occurs while your group is boarding, so if you're in Zone 1, you'll be processed first. Depending on the gate used, boarding can get unwieldy, as they'll hold up signs as the groups change.

***edited to add*** note that the liquids restrictions are enforced at the gate, so your more-than-100ml liquid gotta go.

The only liquid allowed will be any duty free purchases at EZE. If you are connecting from somewhere else, you will not be allowed to bring any duty free liquids.

As an added caveat, if you're on an ATL Int'l - Int'l connection, your checked luggage goes right through (no need to claim and drop) so there's no opportunity to place any EZE-acquired DF liquids in your checked luggage.

Why do some airports in Latin America have these restrictions, while others don't? Is there a trusted airport program or something like that?

The 'not being able to bring your own water onboard' for some flights to the USA infuriates me, especially when they never pack enough on the plane. That and the fact they've already gone through your suitcase at security that's no different than what you get in the US.

Not bringing any "extra" liquids, but is regular, domestic USA type ziplock baggie okay?

I am not sure if the transfer happens automatically. You need to get the "I-t-I transfer" velvet sticker attached to your baggage tag during check-in; perhaps check-in agents pay attention to it and attach it without asking, but I have always asked for it in Lima. Also, the transfer is possible if the second Int'l connection is also operated by DL; in case it is an AF or KL flight or a flight marketed by DL but operated by another carrier, you will need to recheck your bag in ATL.

All true - but at EZE, the agents seem to be well-versed in the procedure.

Agents are very consistent in using the I-to-I tags, however, several times (last time it happened was traveling GRU-ATL-SDQ) my bag was delivered to customs. I only noticed this at the SkyClub and about to board the SDQ flight. They were very diligent to call baggage services, clear the bags through customs, and send them straight to my flight. Before boarding ended, it was already scanned on my flight.