" the American dream where a hard worker in a well paying industry will, in fact, live far better than in any other country."
Why should a decent standard of living only apply to those working in a well paying industry? Shouldn't all industries be well paying, at least to the point of people being able to afford to live? Countries need a variety of industries, skills and jobs to function. If you work hard you should be able to live well, regardless of industry. But in many countries, including the US, working hard & long hours can still leave you on the breadline and choosing between heating your home or fueling your car. The US has huge income disparity and there is a total lack of respect for many employees. This is what people are getting sick of and realising there are other options.
There are multitudes of people living in other countries, doing the same jobs as millions of Americans, living much better than their US counterparts and many of those are immigrants. The US is not competitive for immigrants, it can't even provide all its citizens with the adequate jobs they want. Even removing small countries and the effects refugee crises, there are many countries with higher per capita immigration than the US.
I am in no ways opposed to migration, being a migrant & product of migrants myself, but what the US needs most is decent working conditions, rights & pay. Not only does this solve the employment problem, a higher quality of life leads to improvements in many areas across society, from increased education to lower crime and happier people.