A US citizen with no ID other than a “green card”?? Bizarre to say the least.
Yes.
To go to even to and from Mexico or Canada now one needs a passport or passport card for land travel.
Everyone.
When he tries to use a green card, that is a red flag.
Guy was dumb.
At the same time, if he really is a US citizen he should not have been held four months.
This isn’t the Soviet Union, a lot of people don’t carry, “their papers.” However, when you go to another country, it would highly advised.