Actually, it's not an issue of which terminal is for domestic vs. international. The issue is that in the USA, most travelers don't have their passport checked or stamped in person by government officials when departing the country as a matter of course. (Govt clearance to leave the country is obtained indirectly by the airlines in most cases.) As such, travelers don't legally "depart" the country until their plane is out of US airspace. By contrast, in most other countries (Europe, Asia, etc), when departing on an international flight, one clears exit immigration and is then in a no-man's land in the gate/lounge area, having legally been stamped out of the country. At this point, the traveler has no way of leaving the sterile departures area except by boarding the international flight. In other words, he cannot just walk out the exit door because he has already crossed the border and is no longer in the country. This is where U.S. airports would have a problem, because secure departures areas DO have exit doors where you can just walk out and be on US soil. It would take major reconfigurations of large international airports, and substantial staffing changes, to transform international departure areas into sterile areas, IMHO.


Now, I can see how the USA could reintroduce ITI lounges at select airports (like DFW and maybe ORD) that are set up for that by using the sterile arrivals corridors to escort ITI passengers back down to waiting aircraft AFTER all locally departing passengers were on board and the doors to the terminal concourse were sealed. The issue would be making sure that none of the ITI pax slipped out of the transit area into the concourse because, from there, they could simply walk out of the secure area into the USA without undergoing arrival FIS procedures.