Which u. s. government department is responsible for implementing u. s. foreign policy and diplomacy efforts and plays a key role in integrating the capabilities of the u. s.? the department of state is the lead federal agency and oversees u. s. government coordination and support to a host nation's internal defense and development/coin efforts?

The foreign policy is constitutionally demarcated by Executive Branch and the Congress. Inside the executive branch the department of state commands the foreign affairs agency and the principal adviser of the president is the secretary of foreign affairs. Their activities includes everything developing and implementing foreign policy for the president and for the citizen and tourist trying to visit the US. Among it main activities are creating job opportunities with companies/markets abroad, ensure peace and stability, open dialogues between nations in order to solve common problems such as terrorism, cross-border pollution or the spread of communicable diseases, protecting and assisting US citizen abroad, coordinating and providing support for international activities among so many other concerns.

The correct answer for your first question is: Dept. of State, which advises the President and is equivalent to the foreign ministry of other countries. It also represents the country in International affairs.

Regarding your second question "the department of state is the lead federal agency and oversees u. s. government coordination and support to a host nation's internal defense and development/coin efforts?" The answer to this question is: yes, that is correct.