I'm trying to update my subscription payment method, but the system doesn't recognise my address because it's not in the USA

Welcome to the Community, richard.

Let me present some helpful tips so you can update your subscription payment method in QuickBooks Online (QBO).

When updating subscription and billing details, it is important to ensure that all subscription and billing fields are completed. Additionally, verify the credit card details and confirm that the address for the credit card matches the address in your QuickBooks settings.

If you're still receiving an error message or are unable to update your billing details after verifying the details above, I recommend performing some basic troubleshooting steps, try signing in to your QBO account using a private browser or "incognito" mode. This can help your computer or device run more efficiently by preventing interference from extensions, plugins, or cookies. Here are the shortcut keys for these browsers:

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Microsoft Edge: press Ctrl + Shift + N
• Safari: press Command + Shift + N

Also, clear your cache and refresh website preferences to remove the historical data and access QuickBooks with a clean slate. 

Moreover, you may also want to learn how to manage your QuickBooks Online subscription, whether you need to update the card on file, change your subscription, or just view your billing history. This article will give you detailed steps and information: Manage billing, payment, and subscription info in QuickBooks

Please keep in touch if you have any other concerns with managing your subscription or any QuickBooks-related concerns, richard. Enjoy the rest of the week!