Comment by Symbiote

Fulfilment doesn't have to go through eBay for this.

If I sell a package on eBay.de to a buyer in the UK, I get a customs tracking number to show eBay has collected the required UK VAT. That goes in the form when buying the delivery label and completing the customs (export) declaration.

The EU prepared for years setting this up. It meant all the national post offices updating their systems, and integrating the private parcel delivery companies. It was planned before Covid, then delayed because of the concern for possible disruption.

The USA seems not to have done this planning, and certainly hasn't allowed the months it will take to prepare for it. At least they may have some of the other half of the system, having set that up for exports to the EU/UK.