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.
Disable biometric unlock; you're not required to provide a passcode but you can be required to look at or touch the device. Cross with it turned off.
I don't think the threat of a fine or jail time is real. Even if the agents said that, that's not an actual legal penalty they can apply. They can deny entry to someone on a visa, but they can't deny entry to a citizen or legal resident. They can keep your device, though.
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.