First of all, I don't care about the bay area, I care about the country at large. Secondly, software companies shouldn't be headquartered in the bay area when there are better states. Thirdly, you are wrongfully assuming that they all would leave the US if H-1Bs were curtailed. Fourthly, you don't specify where they would move to and how they could do without access to the labor pool here.

It doesn't have to be a race to the bottom