> — Even if something “suspicious” is found, that is not guilt and no charges can be laid so what is the point!?
I'm not defending this highly disturbing practice, but the point is that it's a political test. If they find anything politically disturbing on the phone, they can refuse you entry.
The theory is that 4th amendment protections are relaxed at the border (but they're not entirely eliminated). [0] That allows them to search your physical property and to request digital access, but it does not override the Fifth Amendment protection against self-incrimination.
However, CBP does not have the right to demand that you give up your passwords as a citizen. They can attempt to coerce you through detention (but if that detainment were prolonged you'd have a solid habeas corpus case).
I'm not defending this highly disturbing practice, but the point is that it's a political test. If they find anything politically disturbing on the phone, they can refuse you entry.