Exactly. The US tech hubs draw heavily from the subset of very talented Americans who aren't seeing the typical dumbed-down part of the education system, and from immigrants, who are over-represented. If anything, they're constantly complaining that they can't find enough talent domestically -- which, yes, is partly "we don't want to pay them enough", but when you consider the costs to sponsor an immigrant, can't entirely be about that.

The small rural high school I attended in the early 80s was unable to find a math teacher able to teach calculus for my junior/senior year, which significantly reduced my college options.