I am in no way an expert in these matters, but based on the info you've provided I don't think there's anything USPS can do... Once your parcel entered customs in Brussels, my belief is that it then ceased to be USPS's responsibility.
This is the info I found from a quick Google search: LINK
This is the info I found from a quick Google search: LINK
ParcelsI think your best bet is to try contact customs... Although speaking as someone who has placed orders with the store and had them sent to the UK, sometimes they can take a unfortunately large-ish chunk of time to clear.
For goods that are shipped to Belgium from outside the European Union, you may have to pay customs duties and VAT. Extensive information is available on the website of the Belgian Customs and Excise Administration.
Couldn’t find the answer to your question? Preferably contact Customs by mail using the button below or call +32 (0)2 572 57 57.
da.leuven@minfin.fed.be
Statistics: Posted by Kingpin — January 22nd, 2024, 3:53 am