Half of Europe does, it's just that everyone talks about the US like it's a special case because those searches happen routinely. It's legal to search a phone without reasonable suspicion at airports in the UK under the Terrorism act 2000 (pre-9/11!)

I really hate that these kinds of justifications almost always ends up to serve as a push for acceptance through apathy of the status-quo, as opposed to fueling that outrage that pushes for positive change.