I am not left, right, center. I am not even American. I am mostly curious why this is seem in center-left but (as I understood) not expected from the right?

I am supposing that and endless stack of problems to solve is always good for any politician. There is always room to blame something/someone and propose something else of there is a problem.

From outside, the discussions over immigrants in the United States seems to shadow deeper discussions on how to fix the rest. It seems to blame the outside world for the lack of internal competitivity while not recognising any of the obvious problems. For example, it is not a matter of preferirng public or private healthcare like here in Europe. It is a matter of getting what makes more sense. Same for environment, trading, taxes, etc.