OK, just for full disclosure I am still trying to collect a large enough body of knowledge on immigration issues to make an informed opinion. That said, I'll let it be known that I am inclined to have immigration be open everywhere. Preferably with other places even being more attractive than the US. This way immigration contributes more to global development, and not just development in the US.
Now with this out of the way, I have to say that if these companies you are talking about are 'raising money', then they have not created any value for the US economy. You are hoping that they will create value for the US economy. When the companies turn profitable, then they will be creating value. Until that point, they are being used to recycle currency, not to create wealth.
Just a little nit pick on your post. The propensity to confuse 'raising money' with 'creating value' or 'creating wealth' is a pet peeve of mine.