There are many unions in the US. My partner is a member of a union and has much better healthcare and, overall, a better benefit package than I do. They work at the state university.

So? Unions also bought and influenced media outlets. They also lobbied. It's not like unions just sat there while management poisoned the country's mind against unions.

Unions were not able to make a compelling case. They had every chance to do so, starting with them being the default option in many industries.

America abandoned unions for a reason. It may have taken a concerted effort by corporate capitalists to get there, but that's not why. "Why" is because more and more people felt that the unions were not a net positive for them.

It can be the case that people didn't feel that unions were a net positive from the 1960s~2000s and now, starting from somewhere in the late 2010s, have begun reconsidering whether unions are net positive. All that needs to change is conditions altering which make unions seem to be a net positive.

Sure. It can even be the case that unions were a net positive before 1960, too. It can even be the case that the gains achieved by the unions are what made conditions less terrible from ~1960 to ~2000, and that the absence of the unions is what allowed conditions to get worse after 2000. (I don't think that's the whole story, but it's a defensible reading of events...)