Political process and culture. In the recent Canadian election there were lots of promises and talk about parental leave (a labour law).
But as a Canadian living in the US, I’ve just come to the conclusion that people here legitimately want different things. I’m not willing to credit “lack of labour laws” to “lack of unions”, because the causation may actually be reversed.
Many people in the US have a deep hatred of taxes. They really support their gigantic military and can’t imagine cutting it by even 10 or 20%, despite this still leaving as the largest in the world. The ACA (Affordable Care Act) was designed to ensure that everyone in the country had healthcare insurance and it was fought all of the way to the Supreme Court and it only passed 6–3. 3 supreme court judges tried to strike down the act that would grant healthcare services to everyone. These are actual people who voted this way in a very public manner.
The US consciousness is deeply ingrained in “bootstrap mentality” where success is just hard work, and conversely that a lack of success means you didn’t work hard enough. Just pull yourself up by your bootstraps.
I don’t see how unions can thrive in a country where vast chunks of the populace simply don’t want them. I mean, people don’t want to pay taxes let along union dues.