Hi OscarC_924,
Thank you for reaching out to us about using the Microsoft Merchant Center! I'm here to help!
At this time, the Microsoft Merchant Center is available in the following countries: the United States on PCs, tablets, and smartphones, and in the United Kingdom, Australia, France, Germany, India, and Canada (English only and excluding Quebec) on PCs and tablets.
However, since you're targeting the United States, we can enable this feature on your account for you. To do so, please reply to the private message I've sent you.
Thank you for your time!
Sincerely,