who does the president appoint to represent the us in foreign countries
The U.S. Permanent Representative, currently Nikki Haley, is charged with representing the United States on the U.N. Security Council and during almost all plenary meetings of the General Assembly, except in the rare situation in which a more senior officer of the United States (such as the U.S. Secretary of State or the President of the United States) is present. Like all United States ambassadors, he or she must be nominated by the U.S. President and confirmed by the Senate.