Let's assume that after years of drastically reduced immigration, America's tech dominance remains unchallenged. Would that make you happy or sad?
If the policy is wrong, it will be far too late to fix it once the results are clear. Foreign founders would simply go back to their home countries (or more reasonable alternatives, like Canada or Germany), and work in startup clusters there.
In about 20 years, I predict the Silicon Valley will be regarded as a startup cluster in the way Harvard is for higher education: the most well-known and prestigious, but only one of many excellent and sufficient options for your needs.
Considering I am in contact with my distant relatives that my great-grandmother left behind in Italy, my answer to your question would be sad.
So, in other words it will be insignificant?
>If the policy is wrong, it will be far too late to fix it once the results are clear. Foreign founders would simply go back to their home countries (or more reasonable alternatives, like Canada or Germany), and work in startup clusters there.
And we'll lose the nth social site, Uber for X, or fad app?
We won't lose the next Uber or Snapchat. We will lose the next Apple or Microsoft.