I successfully closed my UK accounts, and kept my USA & Canada account, but it took about 6 months of begging. It was not easy, and cause much stress.

You have to log into the UK account. You can not do it from your US account. There is a request to cancel the account, but I had a UK accountant that had to cancel on their end, and send a cancellation on their end to Amazon. Then there is a form to cancel it, but it was not immediate.

I had to beg the accountant over and over again, to keep sending in the cancellation, because it was not cancelling. I sent in my request about 20 times. Finally after getting charged thousands from the VAT accountant, who I never used, they finally stopped charging me. It took about 6 months, and thousands in fees for no reason. I emailed support about 10x's as well. I think I finally wore them down, which is what you might have to do.

I try to tell people, unless you sell a millions of dollars a year, don't do it. Sell Internationally from your US account. VAT is no joke, and they want you to raise your price to cover the VAT, instead of charging the customer. When I sell from my US account, the buyer pays the VAT, plus a shipping fee, if they really want my product.

Good luck my friend, just keep at it. They have to know your mad and serious. I couldn't believe it myself.