I can't go in too much into detail about american unions because I'm not a specialist, however I can maybe shine some light as to why the mafia was not too involved in european worker unions.

In France the first worker unions developped from socialist ideas (the biggest ones in France today are CFDT and CGT) with the CGT being directly backed by the communists. These ideals are the opposites of those of a mafia which rely on a liberal model of economy.

Here's an example of how unions in Europe clashed with the mafia:

Right after WW2 (1947) communists are evicted from the government and a massive series of strikes started out. This is something which scared the USA that feared countries like France or Italy might fall to communists and did not appreciate the influence communist backed unions had on these countries which were their partners and which they helped through the Marshall Plan. Towards the end of 1947, the port of Marseille was shut down by communist unions (CGT). This made the USA very unhappy, however it also made the mediterranean mafias very unhappy. Indeed Italian and Corsican mafias as well as Marseille gangs depended on the Marseille port being open to do business (French connection was based in Marseille). For this reason the CIA and local anti-communist leaders asked for the help of local mafia members to help put an end to the strike, which they eventually managed.

This fear of communist unions in Europe was so strong, the CIA and FTUC are actually some of the iniators in the creation of the FO (third biggest union in France now) which's purpose was to create an anti-communist union. To learn more about this you can look up Irving Brown.

Tl;dr: Major worker unions in Europe embraced communist ideals which was bad for the mafias' affairs.

Concerning the first part of your question you might want to have a look at this book