Do you not see the difference between being polite and being obnoxious when you decline the search of a device in your possession? Indeed, the border agents can refuse to let you enter the country either way, but the probability of that happening would probably differ in the two cases.

No, I don't see the difference, because people crossing the U.S. border simply don't have any right to decline searches:

https://en.wikipedia.org/wiki/Border_search_exception

You can decline the search in which case they can decline to let you in the country. The EFF FAQ has more details.

Interesting - I don't suppose you have a link to relevant part of this FAQ?

Sorry, I was on mobile when writing the previous comment.

Here is the lengthy document I remember: https://www.eff.org/document/defending-privacy-us-border-gui...

They can demand a password from you, you can refuse to give it, and they can then decide not to let you in the country. Being polite and respectful in your refusal to share an encryption key can mean less trouble.

A point that might have caused confusion: they can seize your device. The document does not specify what happens if you decline to give the device (as in whether you are arrested or simply declined entry to the country). As far as I understand the references, courts have not had to decide on this question yet.