This is a curious diagnosis of a late 40s law. Consider why average Americans, including those in the lowest rung, vote against pro-union legislation (or don’t turn out for it), as well as the difference between Swedish and American unions.
1947 was one of the first red scares, with for instance then SAG president Ronald Reagan signing explicitly anti-communist statements.
Unions are always assault from capital; they just never really recovered in the US from the red scares.
Outside urban centres and select belts of the country, unions poll poorly. A candidate running on pro-union credentials will perform the same as, or underperform, one who is neutral on the issue. Ignoring the trust deficit American unions have with the public is partly why this situation isn’t changing.
> citizens don't get to vote on individual laws
Most American states have referenda. Even in deep blue states, like New York and California, it’s typically a struggle to get pro-union ballot measures through.
It’s not just some innate thing that Americans don’t like unions.