GP here: And not just contact information, but a legitimate US legal and financial presence.

If you're selling in the US, I need to be able to effectively sue you and win in the US if you sell harmful or illegal products, full stop. So you should have to put up some kind of financial bond and a law firm to represent you. Because mom and pop businesses can't do this themselves, this should be provided as a kind of insurance policy that's just part of the cost of doing business. Heck, Amazon can be that insurance policy if they want.

But right -- if I can't sue you, you should under no circumstances be allowed to sell within the US on a US platform.