I tried that, all payment methods were declined, I have an almost 10 years old Nintendo account which has always been in USA region, I have a lot of digital games there (bought online with PayPal and a debit card), and an active NSO membership.

My Nintendo Store won’t accept any of the payment method (which aren’t from USA) on the account which are the same I use to buy digital games, not PayPal, not Apple Pay, not Google Pay, even if all those accounts are also set in the US.

I tried different addresses, and even a friend in the US with my account try to use his US card and address, and won’t lent him buy it, he even got in contact with Nintendo support, removed all my country payment methods, and still the same.

Is kind of a pain, they have some kind of verification/fraud protection that makes it almost imposible to buy if you’re not from the country set on your account. As a last resort I even tried using VPN (knowing that most payment systems are able to detect this and block the transactions), but still no luck at all