Despite what Michael Bloomberg and the "Partnership for a New American Economy" tell you, there is a debate about skilled immigration.
Some number of skilled immigrants might start companies that eventually employ a certain number of Americans. However, those who don't start companies will wind up being competition for American workers.
Skilled immigration has several negative impacts on the sending countries.
Here's a list of the leaders of the Partnership for a New American Economy. The four mayors involved all support massive and illegal immigration in order to obtain political power. The goals of the others involved isn't hard to guess.
See the links for more information, especially on Bloomberg, Villaraigosa, and Gordon.

Click the image to play a video showing immigration lawyers describing how they use the H1B program to keep Americans from getting some jobs.
"Lies, damned lies, and statistics". Skilled immigration supporters try to mislead you in various ways.