Air and water standards do not encompass the entirety of regulation.
Didn't claim they did, just cited a most glaring example. The lax environmental laws are indeed a major factor in why manufacturers 're-located' there, along with the cheap labor the Red Chinese govt. provides, and of course the tax subsidies our own govt. gives them. The govt. enforces all manner of legalized slavery via its labor laws, they just call them 'employment contracts' and are a distinction without a difference. You can easily figure out why that ties in with having 'illegal residence' laws to help out with those.
Are you indicting the US, China or both? I tend to incline to both but with China being the bigger offender with the blind eye they give to "Snake head" Human traffickers. The internet puts out what amounts to the going rate for annual rental rates of Asian women according to nationality and age. It seems like about every three months some woman poster puts out a thread on the subject along with links but curiously the trafficking of Latin American or European women to the US rarely generates threads.
The Chinese restrict internal travel because it makes it easier on them to distribute jobs and the like, and reduces strains on a given area's infrastucture; no massive mobs racing from one boom town to another. Multi-nationals of course have zero problems with regulating and forcefully controlling labor; they never have, and would have no problems with the U.S. govt. treating workers the same way. They get along famously with the highly regulated Red Chinese way of doing things.
And yes, the slave trade in the U.S. is also a disgrace, but just try and get a budget to fight it out of Congress, and particularly 'conservatives' to vote for going after slave trading effectively; they won't even fund more investigators and auditors to fight Medicare and Medicaid fraud.