What part of the government has the power?

Answer 1

In the US, the Secretary of State is the primary determiner of foreign policy.

Actually the answer to this question is that members of all three branches of government have diplomatic power.

First, the executive branch. Primarily, diplomatic power is concentrated in the office of the President and the Department of State. One of the functions of the President as head of state of the U.S. is to make state visits to foreign nations on behalf of the U.S. Another function of the President is to negotiate executive agreements with the heads of government of foreign nations. The President can also conclude formal treaties, which, because of their constitutional status, must be ratified by the Congress. Constitutionally, treaties can be deemed coequal with federal law.

The Secretary of State, a cabinet position, is the head of the executive department which represents the United States officially and interacts on behalf of the United States abroad. Whereas the President interacts diplomatically particularly with countries and in situations of prime importance to U.S. policy, the Secretary of State interacts with foreign leaders in more mundane and routine situations, although some can be of elevated importance to U.S. policy.

U.S. diplomats and their staff are employees of the State Department. Senior diplomats have the privileges, rights and powers as status diplomats travelling to foreign nations, presenting their credentials to leaders of foreign governments, and residing abroad, as Ambassadors and ministers plenipotentiary, etc. Diplomats and their families travel to foreign nations with diplomatic passports, which require foreign governments to extend to them certain diplomatic privileges.

Members of the military, primarily of the Marine Corps, function in detachment to U.S. embassies abroad in matters pertaining to the physical security of the various U.S. missions abroad.

Secondly, the judicial branch. American federal courts can and do interact officially with their counterparts in other nations through letters rogatory, a legal writ whereby American and foreign courts communicate, make representations, and request certain courtesies and relief reciprocally for litigants and others who appear before American and foreign courts. In this way, judges act in a diplomatic capacity, on behalf of the United States.

Finally, the legislative branch. Congressmen often travel to foreign nations in order to interact and examine governance and other situations in other countries in order to adapt innovative ideas to American governance. As Congressmen, legislators travel under diplomatic cover and thus act as official representatives of the United States in this capacity.