What is the difference between the US government and the British government?

The United States government is a constitutional republic. 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. The British government is a constitutional monarch. The government is lead by a Prime Minister who chooses a other ministers. Parliament makes the decisions not the Queen or King even though ultimate authority lies with the monarch.