Question

In regard to the federal bureaucracy the president of the united states is at the top of the executive branch hierarchy

Answer 1

The president is always top adviser, therefore he is the Head of State of and the Head of the Government of the United States.

Answer 2

He or she is an elected representative of the American people.
and

The constitution makes the president the chief administrator of the federal government.

The President (along with Vice-President) is elected by voting by all citizens, whereas other office holders in the federal government were elected on a district by district or state by state basis.

The Constitution asserts (in Article II, Section 1): "The executive Power shall be vested in a President of the United States of America." The role of chief executive means that he or she holds the primary administrative role in the federal government. We often refer to the staff of the White House as the current "administration," such as the Trump administration (in reference to the current president).