Globalists and the Dems both want open borders. They don't even care about assimilation. They want to destroy borders, cultures. They don't care if the migrants are educated, indigent, or even if they are criminals. They leave all the costs dealing with the migrants to the indigenous population. Most Amereicans would like to maintain our culture, customs, etc and don't want to be taxed to support millions of people who just decided they would prefer to live here for benefits our society offers not persecution in their home country.
Our economy is slowly but surely being integrated into a global economic system. This is really bad for American workers, because now they are being merged into a global labor pool in which they must compete directly for jobs with workers in other countries where it is legal to pay slave labor wages.
Most people don't want unelected bureaucrats making decisions for them The election of DT, Brexit, Italy, Argentina and brazil are all seeing a shift to nationalist parties gaining power. Merkel has destroyed Germany with unlimited immigration policies and she will be soon out of power.