From Michio Kaku[1]: "The United States has the worst education system known to science. Our graduates compete regularly at the level of third world countries. How come the scientific establishment of the US doesn't collapse. If we are producing a generation of dummy. If the stupid index of America keeps rising every year [...] how come the scientific establishment of the US doesn't collapse. Let me tell you something. America has a secret weapon. That secret weapon is the H1B. Without the H1B the scientific establishment of this country would collapse. Forget about Google, forget about Silicon Valley, there would not be a Silicon Valley without the H1B. [...] You realize that in the US 50% of all PhD candidates are foreign born. [...]"
the rest of the video is pretty good too. I recommend watching it.