Which part of "send a giant box of stuff to the US using regular shipping channels and pay whatever duties and/or tariffs are due, sort it out into individual destinations once it gets there, and then deliver with USPS at regular domestic rates" involves this subsidy that you speak of?
You used to be able to get knickknacks on AliExpress (incl shipping) for less than the cost of a US domestic postage stamp. Nowadays it seems like free shipping has a higher minimum, and most of my items use unreliable gig economy services like uniuni for the last mile delivery