> Our provinces have fewer rights, powers and responsibilities than US states.

It's complicated. In theory, US states have more rights and powers ("The powers not delegated to the United States [...] are reserved to the States" [0]), but in practice, the Commerce Clause lets the Federal government do essentially anything that it wants. Canada's provinces are only given control over a specific set of topics [1], but their powers are almost absolute in these areas, since the courts almost never let the Federal government interfere.

So for labour code specifically, US companies need to adhere to both Federal and state labour codes, while Canadian companies only need to follow a single provincial labour code. (There is a Canadian Federal labour code, but that only applies to Federally-regulated companies, and those companies don't need to follow the provincial labour codes)

[0]: https://en.wikipedia.org/wiki/Tenth_Amendment_to_the_United_...

[1]: https://en.wikipedia.org/wiki/Constitution_Act,_1867#Part_VI...