Even with the passport requirement, the US guys at Lukeville are still very flexible, especially driving your own US licensed vehicle back home into the US.Good Luck getting back to the good ol' USA because they check 99% of the time now...don't know for sure what happens if you are not up-to-date.
Maybe someone does?
International airports are a completely different ball game where people without the correct papers are turned back regularly to their country of origin. They have to catch the next flight back.