The answer is simple!!! The jobs you are talking about require High Levels of Education, Americans are by far NOT STUPID, We have a lot of very bright people here, as a matter of fact, most of the discoveries that have changed the World, took place here!! The US is a country that until now, has always welcomed Foreigners, because, this melting pot of Talent and different mentalities made the US the Most Powerful Country on Earth. Now, why don't we have tens of thousands of Very Highly Skilled Americans, the reason why, mostly, is because a 4 year College Degree puts anyone on a $100 thousand dollar+ debt, which takes years to pay, most people just can't afford that. For example, to be able to Study at Harvard or Stamford, it's not almost impossible to get admitted, but, if your parents aren't rich, you are going home probably with a $200 thousand + loans, then, you will need a few more years to get your Masters or PHD Degrees. Another big problem, the US Government doesn't really encourage Students to become highly skilled Professionals, they much rather allow a few thousand foreigners, used them for 6 years, get the most intelectual Property from these people, pay them less, than they would pay a US Citizen performing the same task and send them home. Now, Mr. Trump with the Advice of Stephen Miller, a Jewish descent American, whose genealogy goes back to his great grand father , someone who lost his Naturalization test for u201c being Ignorant u201c and whose ancestors also moved one by one from Germany, his great-grandmother didn't speak a word of English moved to the US and used the u201c Chain Migrationu201d to come one by one here, is the same person now, trying to curb illegal and legal Immigration. His Uncle called him publically u201c A Hypocrite u201c for what he is doing against Immigrants and especially against minorities, forgetting Jews are still fringed upon in the US by most White European Americans. The US Chamber of Commerce has their hands deep into all this Immigration Mess!!! Because they spend hundreds of thousands of dollars to bribe Politicians to keep the Status Quo, but, OBVIOUSLY with Trump, things are not going as supposed to. He hates foreigners even though his own grandmother came here from Germany and his grand father ran from the German draft and ended up in the US, I believe, it was his grandmother who came here and worked as a maid, not speaking a word of English too. Let's talk about bringing ONLY the brightest and most Highly Skilled Workers, it's LAUGHABLE. To make my point, the number of Foreigners to be admitted in the US will be shorter and shorter every year!!! Something huge Companies are not counting on!!!