Anything could happen. To be totally honest, most Americans, myself included, have never been outside of the country, so we don't know.

If I had to speculate based on the news, the fact that he isn't white, doesn't speak English well, and may have no electronics/ questionable electronics, all adds up to a high likelihood of him being detained for an indeterminate amount of time, and potentially being deported to somewhere that no one wants to be.

Honestly they would probably just back-track you because you'll be more suspicious. Idk I'm just theory crafting but customs can look up employment and other data instantly, idk what else