When you cancel a subscription in the App Store, you must wait until the subscription period officially ends before you can change your Apple ID's country or region. This is because active subscriptions are tied to the region in which they were purchased, and Apple does not allow region changes while a subscription is still active.
If you attempt to change your country or region before the subscription expires, you'll receive a message stating that you must wait until the subscription period ends. To check when your subscription will expire:
- Go to Settings on your iPhone.
- Tap your name at the top.
- Select Subscriptions.
- Locate the subscription and check its expiration date.
Once the subscription fully expires, you should be able to change your Apple ID's country or region by going to Settings > Your Name > Media & Purchases > View Account > Country/Region and following the on-screen instructions. Keep in mind that you may also need to update your payment method to one valid in the new region.