If this is genuinely an issue (I never really tried, I just asked a handful of interesting offers if they'd consider making the effort and never really received a positive reaction), why haven’t more companies tried to set up large teams in Europe and Asia?

I never heard anyone say that Google Zurich (a terrible location, work-visa-wise) or Sidney didn't fit the bill. Remote work appears to be common practice — a third of offers consider it, and cools start-ups advertise not having an office.