I looked on the Parcel Force website, and that said that the status was "advised" and it was "forwarded for export" by a "delivery agent" in Chicago on 27/11. I called USPS customer service and the customer service representative said it was probably stuck in customs in the UK and they could open an enquiry form (which I did) but that it would take months to sort out.
Is there any chance that this will ever be delivered? Has it just been lost? I feel quite sad as it was a gift for some friends who just had a new baby, and was some stuff that was quite special