It is merely a theory that explains how free enterprise works. Banks for example, a very important part of the economy, are left out. Some socities do not accept the circular flow model theory. These socities, therefore, choose another economic system other than capitalism. Socialists and communists see the role of the government in a different light than capitalists do.
The United States Constitution states that the Vice President of the United States is the President of the Senate, despite not being a senator, and that the Senate must choose a president pro tempore.
Legislative Branch: the leader of the Senate is the Vice President & the leader of the House of Reps is the Speaker of the House. Executive Branch: the president is the head of state and head of government of the United States of America as well as the commander and chief of the Armed Forces.