I am not sure how you are implying those two things can be seperate. All immigrants have a source. Throughout US history there has been waves of immigration. Where that source is has changed along with the resentment of that source. It is not from any particular source that resentment occurs, but that there is immigration from a source at all.

That view is ahistorical. Anti-immigrant sentiment has always been directed at the source of the immigration. When Chinese began immigrating in the mid-late 19th century, immigration was suddenly a problem and so we had the national origins formula which ruled until 1965.