If your IP address is causing a problem, you can change it here:
http://www.hide-my-ip.com/
Be forewarned that some countries make it illegal to use that site. Check your local laws. I believe Germany bans it for German citizens. So far as I know the US allows it.
Amazon, as well, may not allow its use to avoid their rules.
You could also send your PW back to the packet forwarder to cancel the Special Offers from a US address.
All that said, Special Offers are not really that bad. Maybe the best course is just leave them as is. They do not interfere with reading eBooks.
PW's were originally sold with and without Special Offers. Maybe have your packet forwarder return it to Amazon for a refund and get the proper unit from the start. I paid a premium for my PW without Special Offers and did not have to use the Amazon web site to remove them.