One of the directives the new President has signed is the implementation of a biometric exit system for all visitors to the U.S.
That means, like Schengen, visitors will have to got through exit immigration in the U.S. Not sure how this will apply to U.S. citizens.
This will mean physical changes at most U.S. airports. There will have to be a way for departing international passengers to be separated from departing domestic passengers. Additionally, I'm guessing U.S. citizens will also have to wait in some type of line to show their passports. (Hopefully, Global Entry folks will get expedited somehow.)