Encryption itself is a form of speech. Therefore the govt can't force you to decrypt.

Guarantee is too strong of a word, but this is the concept.

That’s a specifically US interpretation based on US case law. It doesn’t apply in the UK or anywhere else.

US also interprets political bribes as free speech, which is nonsense.

I’d phrase it as the US recognizing that all political support (including money) is speech.

It’s difficult to decide what type of political speech is and isn’t okay, without censoring.

(Said as someone in favor of public funding only for campaigns, but who acknowledges external funding would be a nightmare to police)

You are supposed to have a 4th & 5th Amendment rights in the US. However a Judge can order you to decrypt a drive given probable cause IIRC. There have been cases where Judges have jailed people for disobeying an order to decrypt a drive.