I think that you're not well-informed about the character of U.S. unions. Most are in the trades and manufacturing sectors. Members of those unions are typically right-wing and would be appalled at your characterization. The largest U.S. union, AFL/CIO is hardly leftist.
It's interesting that you mention Communism. Historically, U.S. unions have been vehemently anti-communist after widespread suspicion of the U.S. Communist Party spread, due to developments (mass murder) in the Soviet Union and also due to its overt link with the Soviet international organization (Comintern).
While public sector unions, ---particularly teachers unions and police--- can engage in what could be called leftist tactics and attitudes, your description doesn't fit private sector unions.
Some private sector unions in the U.S. have a long history with corruption, particularly Mafia involvement with meat packers and longshoremen in New York, but that is an entirely different matter.
It's interesting that you mention Communism. Historically, U.S. unions have been vehemently anti-communist after widespread suspicion of the U.S. Communist Party spread, due to developments (mass murder) in the Soviet Union and also due to its overt link with the Soviet international organization (Comintern).
While public sector unions, ---particularly teachers unions and police--- can engage in what could be called leftist tactics and attitudes, your description doesn't fit private sector unions.
Some private sector unions in the U.S. have a long history with corruption, particularly Mafia involvement with meat packers and longshoremen in New York, but that is an entirely different matter.