But... you know that a chinese factory does not need approval by US regulators to run, right? Like... the US doesn't run the whole world and it's not a normal thing that US regulators check out foreign factories, nor should it be.

Now if you get accused of using slave labour... how can you prove that you do not do that? You'd need to prove that the slave-labour-factories don't produce anything that then gets sold to you, right? Because absence of slave workers in your factories is not proof that you don't subcontract a slave labour factory. So you'd need to demonstrate that you've got nothing to do with them. But if you don't work with those factories, you have no stake in the factories that exploit slave labour, so you can't let (foreign) regulators into those factories. Now, even if you manage to do that, one could just turn around and say "Well, then you must use another factory we don't know of, prove that this isn't the case". You cannot prove innocence, you can only prove guilt.