I am a UK resident and customer of amazon.co.uk. I can login to the screen you get sent to after picking one of the ad-free packages, and am presented with a choice of my registered credit cards from which to make the payment.
You should have no difficulty in making a payment, though you will be subject to the usual exchange rate charges for a US$ payment.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.