It is worth noting that the US has been doing digital device searches coming up to twenty years now. I had my phone searched back in the early 2000s, and my most recent US Visa required me to list all social media accounts.

I've even read (but not experienced) reports of GrayKey or UFED being used to download someone's unlocked phone for offline analysis also. Your choices at the border are either: Unlock your phone and MAYBE get let in, or refuse which is best case a guaranteed entry refusal or worse case a 5 ban (for "non-cooperation" as inadmissibility reason).

The US (and UK) treat non-citizens terribly at the border; even with zero history or justification. It is even worse for non-white Europeans.