Hand over to whom? The immigration police that they have stationed at the jetways of all flights out of the USA?-- oh wait, there's no such thing. The airline isn't going to care how someone "got in" to the US.
Thanks! I agree with everything you said, except this one.
Last November, I was boarding a JFK to CDG flight. There were 3 uniformed
US CBP officers checking everybody's passport at the gate area. They had
some kind of handheld computer and sometimes punched in numbers that the
read off the passenger's passport. Although I suspect it was just a random
check? Not really sure what they were looking for.
When returning to the US, I have been asked where I boarded and why there
was not visa or stamps.(which is common if coming back from EU countries)
The officer asked to see my boarding pass and let me go. This probably has
more to due with the fact that my passport was completely blank.
Of course, this wouldn't have made any difference in my original question,
since "Joe" will have his US passoprt as he boards the plane.