Historically, unions in the United States have been strongly anti-immigrant because they were seen as competitors who lowered wages. Anyone who has been on HN long enough has seen the undercurrent of anti-H-1B sentiment whenever the topic comes up and a union would bring that nastiness and racism out to center stage.

No, no immigrants in tech are going to want to vote for a union because a lot of its members think immigrants are part of the playing field that needs to be "leveled".