United Nations Declaration of Human Rights (UDHR) 1948, Article 12: “No one shall be subjected to arbitrary interference with his privacy, family, home or correspondence, nor to attacks upon his honour and reputation. Everyone has the right to the protection of the law against such interference or attacks.”
Privacy is not a right under US law. The US constitution makes no mention of it and the interpretive framework that creates such a right was recently overthrown in the antiRoe ruling.
Privacy is not an implicit right under the Constitution under the new ruling of RvW, but that doesn't mean it's not a right under US law. There are plenty of privacy laws in the US.
Police in the UK have the power to seize mobile devices from any traveler entering the country, and can retain their personal data for as long as they see fit, according to a report from the Telegraph.
They might have the power to, but they don't exercise it[1]. Also, this is about phone as in physical device; it doesn't grant them the right to access the (encrypted) data, does it?
1. Fun fact: the Queen has the power to execute anyone at will.
But hey, just add the US to the long list of countries like Canada, UK, Australia, etc, etc, etc.
Maybe we can come up with a positive list of countries that won't search your phone at the border?