Samantha Power has completed a personal goal she set when becoming the U.S. ambassador to the United Nations in August 2013: She has visited the missions of the 189 countries the United States has diplomatic relations with – and she recommends that her successor Nikki Haley does the same. Power’s last courtesy call Friday morning was to the two-room mission of the Pacific island kingdom of Tonga and its Ambassador Mahe’uli’uli Sandhurst Tupouniua, who surprised her by saying “Our 18th century constitution, I understand, is the second oldest to the United States.”