Major differences: no ID checks at security, and boarding passes aren’t scanned by humans in make-work jobs, no shoes to be taken off. If it was mostly the US i

Major differences: no ID checks at security, and boarding passes aren’t scanned by humans in make-work jobs, no shoes to be taken off. If it was mostly the US imposing on the rest of the world, you would see separate security for US flights in airports whose layout allow it (and international flights to USA already have lots of annoying extras, like adversarial interviews at the gate (e.g. AA at LHR), and hand searches of cabin luggage).