I think that some domestic manufacturers will abuse labor and pollute, you will never have 100% compliance. However it is far easier to police things here then somewhere without our regulatory framework. If Nike could get away with child sweatshops in the US, why did they bother moving abroad?
Sure, they want to roll back all those protections but we don't have to. And more to the point, why doesn't the US party that champions labor rights and environmental regulations want to move manufacturing back to the US? It's very easy to say you support factory worker rights when you don't have any factory workers.