On: Multiple Passengers Skipped Customs on US-Bound In...

[alexanderchr]

US does not check your passport when you’re leaving the country

[midasuni → alexanderchr]

It does check the passport information provided by your airline, which is how they inject if you’ve overstayed.

If that process gets screwed then you can be in a world of hurt next time you visit.

[flemhans → midasuni]

Can you still leave by land to Mexico without any trace?

[fmajid → flemhans]

There is a classmate of my daughter (UK) whose family went to vacation in California. On a whim they decided to visit Mexico, but had left their passports at their San Diego hotel. They were allowed into Mexico without a passport and had an, ahem, interesting re-entry to the US. I’m surprised they were actually allowed back after several hours.

[Gibbon1 → flemhans]

Nothing stopping you that's for sure.