[Scoundreller]

Americans can still visit Canada without a passport by land as long as they can satisfy proof of citizenship.

It’s technically the US that requires Americans to have a US passport to re-enter USA. Not sure what they do, can’t refuse a US citizen entry into USA but I guess they could give you a hard time.

[cmrdporcupine]

On a work trip to the US recently I lost my passport for a bit and spent some time frantically searching what would happen if I showed up at a land crossing back into Canada without it. TLDR they would have given me a hard time, put me through the ringer, but ultimately would have to let me back in assuming all my other ID, references, etc. check out. I'm sure it would be highly unpleasant.

Airlines of course would imply have returned to board me without it.

Luckily I recovered it (bless you, friendly helpful people at the Sioux Falls airport) before my return flight.

(Replacing it would have had me stuck there for many days and requiring me to travel to Minneapolis or Chicago and beg for mercy at the consulate.)