Generally speaking, you have to keep in mind that in the US many employers see employees as subjects (much like slaves),especially when it comes to bluecollar work. There is no national legislation that draws a clear line.
No coincidence here that the term human resources was invented for labour. They are resources that can be exploited until they can't be further exploited.
It weirded me out big time when I first heard people talking corporate-speak saying "we need a resource for ...". Took a while to proccess , apparently they meant a person, I was thinking "hmm.. Wouldn't it be better to hirr someone, what resource can do this? ML? SaaS service?"