Why is Argentina listed under my Payment options?

For this you would need to contact support and they can help you trace it. (800) 469-9269 if you're in the US/Canada or
http://support.xbox.com/contact-us

Just wondering, if you are from Argentina, why do you want to Migrate to the US?

This will likely cause other issues and you will need to specify actual US address information etc for any payment options and also run into issues with region specific downloads.

Argentina is a supported country, so why change. I Personally would advise against it

Yes, my billing address is Argentina and the payment option is for Argentina too, the thing is that when I'm trying to change my gamertag I got send to the US XBOX site to pay for the gamertag change, from the Argentina XBOX site.

I have a payment method and everything, but everytime I try to pay with my Credit card is asking me to put some US address info and the Region box is greyed out, so I can't change it.

Hi At1ch, my name is Rodrigo. I'm an Independent Advisor and a member of the Microsoft community and I'd love to assist you today.

I am sorry to hear that.

Is your Account and billing address also from Argentina? Are you currently living in Argentina?

This may be a regional block.

Have you tried to add your payment method via the website?

Please, follow these steps:

Sign in to the Microsoft account you want to update.

https://account.microsoft.com/

Go to Payment & billing and select Payment options.

You can add or edit payment options here.

Source: https://support.xbox.com/help/subsc...es/manage-payment-options-and-billing-address

I hope this helps.

Remove payment method

• Note: Payment options used to pay for a subscription can be edited, but can't be removed until you
  change how you pay for the subscription. Subscriptions or other services associated with the payment option can be found next to Card info.
  
• Online:
  
  • Sign in to your Payment options with your Microsoft account.
  • Choose a payment method, and select Remove.
• On Xbox One:
  
  • Sign in to the Microsoft account associated with the payment option to remove.
  • Press the Xbox button on your controller to open the guide, then select
    Settings .
  • Under Account, select Payment & billing.
  • Under Payment options, scroll right to the payment option you want to update, then select
    Remove.
  • Select Yes, Remove to confirm payment option removal.