The situation at the U.S. border re phone privacy is exceptionally good. In most countries this isn't a live issue because you have no such rights and everyone would laugh at you for asserting them. There are exceptions, perhaps Germany?
In Britain they'll throw you in prison for refusing to give them your phone password, and if you do they'll throw you in prison for the wrongthink tweets they find on your phone.
Should Americans be subject to search-for-no-reason at their own border? No, and I hope that as these border issues work their way through the legal system this will get sorted out. Please note that the CBP can say whatever they want about you having to give them a phone password, but you don't have to. They might keep your phone for a while and fuck around with it.
I gave the example of the U.K., a dystopian privacy violator. The U.K. is in Europe.
The entirety of Europe would not come close to making a majority of countries. Even if I grant you the "entirety of Europe", I bet I'm still right that most (i.e., more than half) of countries reserve the right to search your device at the border, and will compel you to give the password.
In the U.S., I believe you are covered by your 5th Amendment self-incrimination protections. I have some recollection that there are situations where authorities will compel you, like if you're not the one being accused of the crime.
Should Americans be subject to search-for-no-reason at their own border? No, and I hope that as these border issues work their way through the legal system this will get sorted out. Please note that the CBP can say whatever they want about you having to give them a phone password, but you don't have to. They might keep your phone for a while and fuck around with it.