>most of the foreign born workers in silicon valley are people who immigrated to the US as children

Where did you get this stat? You're calling others liars while posting questionable stats yourself.

A lot of foreign born workers are not H1B because they got their green cards or citizenship. I'd safely say a majority of them were H1Bs till recently. Till 2008, getting a green card for any country was not a problem. It has gotten a lot worse since then.