Hilariously there is an agreement by the US that Greenland is Danish.

In proceeding this day to the signature of the Convention respecting the cession of the Danish West-Indian Islands to the United States of America, the undersigned Secretary of State of the United States of America, duly authorized by his Government, has the honor to declare that the Government of the United States of America will not object to the Danish Government extending their political and economic interests to the whole of Greenland.