Historically the US has not had much "exit control".
For example leaving the Schengen area it's obligatory to go through "exit immigration" and get your passport stamped. Leaving the US, you show your passport to the airline, but usually there is no formal immigration check at all.
Yeah, once upon a time you had to return your actual I-94 stamped to your passport to the airline, but today this is done automatically on the background
Every time I've crossed from US to Canada there's been zero interaction on the US side. Just drive up to the Canadian gate house and show papers.
Especially by land. I've walked into Mexico at an official crossing with zero passport / papers check by either side. In general land and sea travel can have differing rules though, where international air travel is governed by a set of international agreements with standard rules. For instance the full passport book is required for all international air travel.
You will get your docs checked about 10 miles inland Mexico. There you will go through customs and immigration. The border zone is treated differently in Mexico. Mexican customs is very strict: two laptops and you’re taxed 25% on the second one. Technically you can’t bring an iPad and a laptop without paying taxes.
IIRC, [a long time ago?] you MUST give a piece of paper to a guy/gal near the exit, so they remember to mark your exit in the database. I don't think they check too much, just collect the pieces of papers? (I don't remember the details, but if there was a scary warning if you forget to give it and they forget to update the database.)
This is part of the Canadian border control in my experience; i.e.
- Arrive in Pearson
- go to passport control, scan passport at kiosk, kiosk spits out receipt
- you flash receipt to a border officer at the stairs out of passport control
- go to baggage claim
- get bags
- go to customs
- hand passport with receipt to officer at customs
- welcome to Canada
I haven't had that experience when leaving other countries bound for the US; like GP said, I've had to show my passport to the airline to board, but I believe that's to fulfill the requirement that they made good-faith effort to ensure I'm capable of entering the US.
That’s because the airline updates your I-94 for you. If they don’t you risk overstaying. There is a website you can use to validate that they did everything correctly.