>The hollowing out of the middle class in the US isn't because of immigrants, it's because of a sustained campaign by capital to reduce the power of labor
Importing cheap foreign labor to undercut unions and lower wages is one of the spokes of the wheel used by capital to reduce the power of labor (and always has been).
Much the same as in a strike when workers get mad at scabs. The person right there in front of you is looking out for their own best interests and in those circumstances that is to your detriment.
Capital uses immigrant labor partly for simple price reasons and partly because those workers interests really are different from the locals and their lack of local connection makes them a viable slow motion scab workforce.