I personally know one CEO who runs a 80 Mil./year company in the USA, has 250 employees (3/4 are US citizens) but only received a green card or allowance to stay longer then one year in the USA 10 years into the business.
That said, you can't compare the USA with the European immigration laws. As an example, there are many Americans living in Berlin. The way you can live in Berlin is by flying to Berlin and show up at the immigration within a week and tell them that you want to move here, pay taxes and work. It is even easier if you already have an employment.
Additionally, there is something like a "Language" & "Artist" visa in Germany. Under these visa's you can simply stay and live here. You can even build businesses and start employing people.
That's Germany. Want to live in Denmark? Same there. Want to open a business and live in Switzerland. Go register yourself and work. Right, you cannot vote and don't have a nice "credit" but at least you are given the chance to build something.
Now, if there would be a startup-visa in the USA, I'm sure there would be many willing to move and try to build a business in the USA. But as it is now, you can't. I'm not taking way jobs from any US citizen, quite the contrary, we are hiring people and try to contribute to the US system.