Cannot add a new credit card on payment preference menu

Hello.

Perhaps AWS accounts issued by AWS Korea cannot be registered with US credits.
The following document describes the credit cards that can be used with AWS Korea's AWS account.
https://repost.aws/knowledge-center/accepted-payment-methods

Regarding changes to AWS Inc., I think it would be best to open a case with AWS Support under "Account and billing".
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html

Hi there,

Thanks for reaching out.

Our Support team can assist with some guidance on this. You can reach out to them by opening a support case here: go.aws/support-center

Regards

— Reece W.