Paul Graham has written a great essay describing the conventional wisdom about the intellectual nexus that is Silicon Valley. One aspect he emphasizes is immigration:
I doubt it would be possible to reproduce Silicon Valley in Japan, because one of Silicon Valley's most distinctive features is immigration. Half the people there speak with accents. And the Japanese don't like immigration. When they think about how to make a Japanese silicon valley, I suspect they unconsciously frame it as how to make one consisting only of Japanese people. This way of framing the question probably guarantees failure.
A silicon valley has to be a mecca for the smart and the ambitious, and you can't have a mecca if you don't let people into it.
I've written before that the effective workspaces I've seen all involve a mix of workers from all over the world. Making people work with only people who look like each other and have the same accents is much like only allowing marriages within one's own clan. You get better matchups if you let people date more widely.
The same is true for conferences. Ideas feed back on each other, with multiple sparks contributing to starting the fire. It often takes more than one good idea to make progress on something. Any of those ideas alone doesn't get you part of the progress. It gets you none. Concentrating people together is an essential ingredient to having a productive conference.
Unfortunately, border control, xenophobia, and general empowerment of the police have increased with every U.S. president since the fall of the Berlin Wall. You wouldn't know it from the news or from the talking heads, but if you do some brief web research you can verify it is true. The current president brought us airport gropes and is also responsible for the line, "Because of recent circumstances, the underwear was taken away from him as a precaution to ensure that he did not injure himself". I don't detect any trend in a positive direction.
I'm spitting into the wind here in the hopes that any change must start somewhere. Xenophobia is not just wrong, and it's not just unpleasant. It's making us dumber and poorer.