Greetings kappa,

As 2 Many Miles mentioned, DFW has a "sterile" in-transit lounge. I haven't seen one or heard of one at any other airport in the US, but perhaps that's because I've never connected from an inbound international flight to an outbound international flight through any US airport, accept DFW.

AA makes a strong grab for México to Latin America travel, and DFW serves as a good hub for this due to it's proximity to the major Mexican markets. Also, AA does well on deep South America-Japan traffic, too. Many Japanese businesspeople connect in Dallas for flights to São Paulo and Santiago, since the overall travel time is less than connecting via New York . . .

I would assume that MIA can handle "in transits", but I don't know for certain . . .