Massive unskilled immigration has had a highly negative impact on the U.S. as a whole. Massive skilled immigration isn't much better:
Impacts on native-born
Description by uploader: Immigration attorneys from Cohen & Grigsby explains how they assist employers in running classified ads with the goal of NOT finding any qualified applicants, and the steps they go through to disqualify even the most qualified Americans in order to secure green cards for H-1b workers...
A number of skilled immigrants might start companies that end up employing some number of Americans, and proponents are eager to trot out statistics backing up their sales job. In some cases those statistics might be skewed: some of the companies mentioned might be very small or the role of immigrants in the company might be only partial. For an example of highly creative math by supporters of massive skilled immigration, see the misleading claim by Gary Locke and Carlos Gutierrez (link below).
Those skilled immigrants or visitors who don't start companies or who don't go home will serve as competition for Americans, especially older workers. In some cases, companies use H1B workers to keep wages low or drive Americans out of work; see the video to the right.
Most of our elites who need low-skilled labor have an attitude that boils down to: "let an illegal alien from Latin America do it." Their thoughts are similar when it comes to high-skilled technical labor: "let an immigrant or visitor from India or China do it."Neither of those are healthy for the U.S. There are over 300 million people living in the U.S. with a very wide range of skills. Supporters of massive skilled immigration need to spend more effort ensuring that Americans go into technical fields, rather than seeking an easy (and lower-priced) fix. The U.S.'s technical achievements in past decades were obtained with much less high-skilled immigration than today.
Modern-day colonialism and braindraining the world
Massive skilled immigration from other countries to the U.S. amounts to braindraining those foreign countries. A relatively small number of people moving from India or China might not have much impact on those countries, but the same isn't true of countries in Africa, the Caribbean, South America, or large parts of Asia. Already struggling Third World countries need all the smart, capable people they can get.
Massive skilled immigration is in effect an updated form of colonialism. In the past, European countries would raid foreign lands for their material riches. The modern-day version is to "raid" those same countries for their more able citizens. In the long-term, the impacts of their version of colonialism will have many of the same impacts as the old colonialism. For instance, braindraining foreign countries now might result in a much larger immigration of those "left behind" in those countries later, might result in a greater demand for foreign aid by those countries, might lead to wars and conflicts, and so on. China and India are going to be two of our biggest competitors in future years, so from one perspective braindraining them might not be such a bad thing from our perspective. In a way, taking their best and brightest is a form of very soft commercial war on those countries.
Skilled immigration proponents (many of whom are simply paid hacks) only tend to look on the bright side, like other salesmen. One downside they consistently ignore is the fact that many skilled immigrants might buy into the American concept of making money, but won't buy into other American concepts. Some or many coming here might remain loyal to their home countries, and some of them might even be spies or willing to engage in espionage for foreign companies or their home countries. Some of those immigrants might form a political power base for their home countries inside the U.S. and for home-grown or imported ethnic demagogues and others who seek race-based power.