It is still possible to disappear into someone else's culture, to leave the global-citizen bubble behind. But in my experience the people who do are exceptional or eccentric or natural outsiders to begin with — like a young writer I knew who had traveled Africa and Asia more or less on foot for years, not for a book but just because, or the daughter of evangelical missionaries who grew up in South Asia and lived in Washington, D.C., as a way station before moving her own family to the Middle East. They are not the people who ascend to power, who become the insiders against whom populists revolt.
Whereas once I began attending a global university, living in global cities, working and traveling and socializing with my fellow global citizens, my experience of genuine cultural difference became far more superficial.
Not that there's necessarily anything wrong with this. Human beings seek community, and permanent openness is hard to sustain.
But it's a problem that our tribe of self-styled cosmopolitans doesn't see itself clearly as a tribe: because that means our leaders can't see themselves the way the Brexiteers and Trumpistas and Marine Le Pen voters see them.