Hello. My name is Michael. I can help you with your question.
On the Manage Your Kindle page on http://amazon.com, you'll see a link to Country Settings over on the left, you can check and change it there. Make sure the address and country that you have there are correct. If you do change it there, the results will be reflected on your Kindle automatically. Also make sure that you have a default payment method that is valid. This error can come up sometimes when the default card on the account has expired. If there is no form of payment, or if the only form of valid payment on file is a gift card balance, it will often give an erroneous error about country.