Instead I would argue that if the Americans opened their borders, a huge fraction of European tech workers/professionals will relocate there. I'd say that, as middle-class persons, they wouldn't subject themselves to the torture of getting a visa, which may also partially explain the rise of Berlin as a tech hub after Brexit.

To give an example: I was among the first airbnb users when it started. In the past few years I used booking.com more because I liked both their website and booking experience better. And yes, they offer private accomodation. Booking.com improved a lot while airbnb stagnated. I admit that I am not the target audiance for the airbnb "experiences" feature though.

Where are the HQs of Qualcomm, AMD, Intel, Nvidia located? Yes, everyone talks about Uber et al and indeed those companies barely add innovative ideas compared to the innovation that is needed to increase a CPU's performance. Uber et al instead mainly do a better job at extracting money from their extremely good market positions than the hardware companies do.