>>A sizeable portion of Trump's base believes that they are in danger of becoming a minority in "their own" country and will sidestep the economic benefits of immigration to retain a demographic majority.
Actually they are simply pissed at that fact- since the end of slavery and colonialism, life has gotten simply too hard.
Also you have to live in the situation now where you are continually reminded you are no racial superman, and some one you thought was way beneath your station is now routinely beating you in highly intellectual activities.
This is not new to the US. Bulk of Indias current social friction problems happen because the previously lower caste people are doing well off in life now. Now economy might be a growing pie on the longer run, but on the shorter run, its just competition for limited resources at the end. If you previously were a upper caste person albeit not very capable, you could still succeed easily, given only your castes were allowed to study and prosper. Today with more people having an opportunity to compete, you just don't stand a chance. Now imagine being a upper caste person who only until recently had to merely exist to succeed to now having to compete and routinely be beaten by people whom you think are beneath you.
Things don't work well.
To those seasoned to privilege, equality feels like oppression - Internet Quote