Sure, they'll remain outside the US as a nucleation site for new startups that could have in theory challenged US dominance in technology startups. But the US controls the financial energy. They won't get anywhere.
Startups will survive large-scale institutional bigotry just fine. In fact: some of them will even profit from it.
Sleep well!
Not sure what the reasoning is here. How is YC doing anything to block people from starting companies? You don't lose anything by getting rejected from YC, other than the few days spent applying.
To be a bit simplistic, I think Thomas' point is that the likelihood of tech startups outside of the traditional US-centric startup ecosystem succeeding is very low, due to lack of funding and the general consequences of being an Outsider to the Silicon Valley elite.
YC's role in it is, of course, being one of the most influential players that control which ideas get funded/attention, and which do not.
Even physically outside of the US, the startup ecosystem is still overwhelming reliant on US money. Which is to say even if there is an appetite for funding founders in these disfavored countries, regulations (or simple politics) may prevent it.
That said, I do disagree somewhat - US/European money is not the only source of venture capital dollars. I suspect at least some of the founders we're losing here will be able to start their companies with Chinese money. The loss of this talent pool will contribute - in a small way right now, but snowballing as time goes on - to the loss of US-centric economic hegemony.