That seems... suboptimal.
All it takes is a corridor from arrivals to departures to allow people to leave again on a different plane out of the country.
Some US airports and airlines are like that for some flights (e.g. international delta flight to Detroit and then onward to Canada). Finally US customs figured that there’s less to worry about if you just hold onto my bags instead of forcing me to pick them up.
Yes. There are some details at the following article: https://en.wikivoyage.org/wiki/Avoiding_travel_through_the_U...