There are two assumptions here that I’d like to point out: that the US labor laws are the best worldwide, and that there is an inherent problem in other countries that would be solved if they just adhered to the US laws.
US historically had, and still has a large number of cases (either legal or just public discourse) of employers treating their employees unjustly, unfairly or with malice, despite all of the legal protection that US provides. There are always edge cases and loopholes. That said, I do believe that to an extent, the precedent based legal system of US trumps European style jurisprudence systems.
Secondly, there is no evidence that by and large the workers are treated better in the US, or that other counties are clearly inferior. International employee engagement is pretty close to the world average in most modern countries.