I know some Eastern Europeans that told me they were treated like garbage in Germany, but as rockstars in the US. YMMV
I think the discussion is about society in general (healthcare, education, safety, work hours, leave from work, etc. ), not about how a person is treated in their individual workplace.
Europeans tend to be nationalist and if you're from the "wrong" nation you feel that. In America you won't be treated with more respect if you're from Denmark and not Poland. So that's an aspect.