I have done the DFW, or MIA to EZE a few times over the past few years. Once in first, 5 times in business, and twice coach.
I travel with a small roller bag with clothes and a leather legal sized bag with all my expensive electronics. I have never been looked at twice in any class of service. I have always gone onboard before the kettel herd.
My last trip was in first on the 777 and this woman had two bins in first taken up with three bags and coats!
My leather legal bag also never gets scrutiny on a crj-700.