One thing I realized as I was leaving Guangzhou (China) heading to South Korea: the United States don’t care when people are departing for international. There’s no customs check, there’s no immigration check. America is probably so ecstatic at you leaving the country that they don’t want to spook you into changing your mind with additional barriers.
The only stamp on your non-U.S. passport when you visit the States is the entry.
(Countries I’ve visited) China has immigration control on exit. So does, Thailand, Japan, and Taiwan. This creates a need for travelers to get to the respective airports earlier. The security check presents enough of a choke point - why add another one? Homeland Security - or whatever a country’s equivalent - should only care about what’s coming in. You know, protecting the homeland. It’s the destination country’s problem to handle if a traveler ends up being the unsavory kind.
Surely a flight manifest is enough data for a country to determine if a person has left the country. Unless of course your name is Carlos Ghosn, and you had to smuggle your way out of Japan in a cargo box.
The way America handles this is the right way - immigration upon entry only. Unless of course the government of a particular country wants to prevent its citizens from so easily leaving its borders. Though even North Korea wouldn’t need immigration check upon exit? Because I am (hopefully correctly) assuming that there isn’t an airline in the world who would sell/operate a flight out of the upper Joseon peninsula to a North Korean citizen.
Look at that, America doing something outside of international norms, but it’s actually good.
Through the looking glass.