Here in the UK, I'd say Starbucks tastes of nothing. Hot brown drink. Their ground bags you can buy and take home are equally a non-event. Not sure why people rave about it. Coffee is some of the worst I've had, not withstanding UK McDonald's.
Only according to Americans, tbh, and often ones who have never visited.
Ones who have visited the UK, when asked where they ate, often ate at hellish tourist traps or absolute shit tier chain pubs like Wetherspoons or Greene King.