Most Americans have little learning about the history of unionism and labor organizing overall, just lots of prejudices on many sides of the issues. Rich Yeselson has written a long article on the decline of unionism in the US following a vast wave of union strikes and other work-related activities following WWII, culminating in the passage of the Taft-Hartley bill in the latter part of the 1940's. Membership in unions stopped growing for the next two decades, newer workers were less inclined to join unions as they experienced decent working conditions and incomes during those years. Essentially they were riding on the coat-tail of unionized workers.
Union membership plummeted after 1980, especially in the private sectors while workers' incomes stagnated and actually fell relative the the gross national product.. Does unionism have a future in this globalized economy.
Here is a link that might be useful: Fortress Unionism