You are unable to link a Nintendo Network ID to your Nintendo Account because the country doesn’t match.
Error Message: This account cannot be linked. The country of residence registered with this Nintendo Account does not match the country registered with the Nintendo Network ID.
What to Do:
Access your Nintendo Network ID (NNID) settings on a Wii U or Nintendo 3DS family system, and check to see whether one of the following issues applies:
NNID Birthdate Under Age 13 - You cannot link a Nintendo Network ID belonging to a user aged 12 or younger. You must be at least 13 years old to create a Nintendo Account, and the NNID date of birth must match the Nintendo Account you’re trying to link to.
NNID Country Doesn’t Match - You cannot link a Nintendo Network ID if the country of residence setting does not match that of the Nintendo Account you're trying to link to.
Situation Not Resolved:
If the steps above do not resolve your issue, please contact our Customer Support.