> This idea that we better let-in hordes of immigrants for fear of not having businesses launched or any innovation is, well, repulsive. That would mean we are a wasteland of a country, and need to be rescued by immigrants, which clearly isn't the case.

Go to any research lab in the US; you'll probably see more immigrants than native-born. Far more, in many places. If America cancels visas and closes borders, it will still launch businesses, it will still occasionally produce a unicorn, but it will be crippled in basic science.