...except at border crossings (which may be at a US border crossing or at an international port of entry like an airport gate where US customs has a checkpoint).

U.S. Customs and Border Protection (CBP) may search any electronic devices without probable cause at these points.

see https://informationsecurity.princeton.edu/sites/g/files/toru...

and

https://www.cbc.ca/news/science/usa-border-phones-search-1.4...

Canada doesn't behave this way - https://www.harrisonpensa.com/new-limits-imposed-on-border-s...