the red scares (in the 1910s and 20s, and in mccarthy era, but also it never really ends) directly explicitly criminalized communism and being a communist, and forced the purges of communists and anarchists from the ranks and board of every union, every civil rights organization, every school faculty and schoolboard, every local government position, and even in media and entertainment; purging any and all militance. The DoL makes deals with liberal remnants who agreed to purge the communists, and the ones that didn't were maligned, marginalized, criminalized, punished, arrested, crushed. This predictably left in its wake in the unions complacency, class collaboration, and corruption, which is why organized crime cozied up alongside the more unsavory class collaborators starting in the 50s, which added to the reactionary politics.

Any time any class consciousness and obstructive action raised its head, they were crushed. Reagan crushing the airline union and thatcher the miners unions was the death knell and last gasp of the any old unions' agency in working class struggle. these labor unions being what they are now is much more a legacy of all of that than anything else. Now the only good unions are the independent ones and militant dual-carding ones like the IWW. Teamsters aren't even the worst. The AFL-CIA--er I mean AFL-CIO literally flew to LatAm and Europe, most impactfully to Brazil and Poland to train their reactionary unions to undermine communism (including Poland's infamous Solidarnosc).

You also still have to fill out forms that ask if you're a communist or are/have been a member of a communist party for many governmental forms. Even citizenship applications. you can be denied for being a communist.