>The United States is one of just a handful of countries — others include India, Pakistan, Suriname, and Papua New Guinea — that have no national policy guaranteeing workers paid annual leave. (It’s also among the few with no federal laws guaranteeing paid parental leave or paid sick days.) Any benefit offered to workers, like paid time off, is entirely up to the discretion of private employers.

It's not "up to the discretion of private employers". It is up to the contractual arrangement between an employee and his employer.

The USA is a huge place. It isn't obvious to me that there should be national laws for things like this. This is exactly the sort of thing you'd expect to be set on a state-by-state basis.