The federal government is composed of three distinct branches: legislative, executive and judicial, whose powers are vested by the U.S. Constitution in the Congress, the President, and the federal courts, including the Supreme Court, respectively.he government was formed in 1789, making the United States one of the world's first, if not the first, modern national constitutional republics. The United States government is based on the principle of federalism, in which power is shared between the federal government and state governments.