[ubernostrum]

In the US, large international airports don't work that way.

Yesterday I had a purely-domestic itinerary out of Philadelphia -- which is an international hub for US Airways/American Airlines -- and while waiting on my flight I wandered in and out of the international terminal several times without facing any additional security (I like watching the larger planes come and go, and the lounge in that terminal is nicer).

Which is the standard way international airports work in the US. There is no concept of "once you cross this point, you have to clear customs again to exit the terminal" here.