[jeanjogr]

I guess the main difference is that in the US (as far as I understand) there is no official workers representation outside of unions, thus some characteristics of workers' representatives are done by the union in the US (you get represented even if you did not vote for them).

Much like the role of the party and State organs in one-party state vs many parties democracies. In the former the roles are much more muddied between the two.