> you have to realize that there will be fewer such startups if a tax on unrealized capital gains is passed, and that VC activity, along with the future startups chasing their money, absolutely will move to countries without such a tax.

That's a bold claim. The tax-averse amongst us say that, but in my experience investment flows to the best ideas / best distribution / best businesses. If those people are in the US because they're citizens, the capital will flow to the US, and investors will take the hit.