The EU mandated it, and it’s easier for the websites to display it globally, so that’s what they do.

That's a very misleading way to phrase it. The EU didn't mandate these banners. The EU mandated getting permission from users before a site can use tracking cookies. Sites that don't use those kinds of cookies don't need to do a thing.

Sites started putting the banners up in part because they didn't want to stop tracking users, and in part to make things annoying enough to users to try to get people angry about efforts to help people protect themselves.

The EU now resembles someone who masters theory but consistently fails in practice.