Microsoft AppSource Country Locked to USA or Wrong Country
The AppSource commerce portal will auto-fill the country for billing based upon the Azure tenant's original creation country.
Once an Azure (or Office 365) account is created, the original country cannot be changed. User licence country settings and company address information is not relevant to the country shown by AppSource.
To find the country setting of any AAD user's tenant, go to this URL when logged in as that user: https://account.azure.com/Profile
You will see a window that shows the country information:
How to buy AppSource services if the country is shown incorrectly.
The AppSource portal will process the order, but will be in the currency shown. Go ahead and enter the address information as required for the credit card ignoring the country setting, the country information will not be provided to the credit card company when the transaction is sent for approval.
Although the currency will be incorrect and the card may be charged in the currency shown (e.g. USD), the transaction will succeed and the AppSource trial will be provisioned.
This issue has been escalated to Microsoft who are aware and have logged the development task to provide a resolution to this. They have not provided any estimated time for a fix.