Wuth a rapidly expanding industrial economy in the second half of the 19th century, why weren't there as many adherents to early Communist political ideals, if not more, than in Europe?
Race really undermined the possibility for even a strong, independent labor party a la Britain.
I would also not underestimate the strength and patronage of Democratic political machines set up in urban centers for immigrants, which existed very early.
I have a suspicion that the fact that Americans were the wealthiest people in the world up until the 1960s played a bigger role than racism. The timing is off if you want to blame race, as well; the Great Migration (the move of southern blacks to northern urban centers) really only took off in the 1920s, but it's not like the Socialist Party was booming before then.
Not necessarily. There was racism against a lot of peoples we'd consider "white" today. Ask an Italian-American.
Or Irish-Americans for that matter. Basically you had to be the "right" kind of white (i.e. Protestant)