The British government is a parliamentary constitutional monarchy. The king is the head of state, the supreme magistrate, the commander-in-chief of the armed forces, and the "supreme leader" of the Anglican Church, and formally has the power to appoint and dismiss the prime minister, ministers, senior judges, military officers, governors of the territories, diplomats, bishops, and senior clergy of the Anglican Church, etc., and has the power to convene, stop, and dissolve parliaments, approve laws, declare war, etc., but the real power rests with the cabinet. Parliament is the highest judicial and legislative body and consists of the King, the Upper House and the Lower House.

The political system of the United States is a constitutional federal republic and adopts the principle of separation of powers, delegating the executive, legislative, and judicial branches to the president, Congress, and federal courts.

Differences between the two:

(1) The parliamentary system of democratic republic is a form of political organization in which the parliament is the center of the country's political activities, and the organs of state power and the head of state are elected by the parliament and are responsible to the parliament. A parliamentary constitutional monarchy is a form of political organization in which a hereditary monarch is the head of state, and its powers are regulated by the constitution and subject to certain restrictions.

(2) The conditions for generation are different. The parliamentary democratic republic was the result of a relatively thorough bourgeois revolution, while the parliamentary constitutional monarchy was the result of a compromise between the bourgeoisie and the feudal forces.

(3) A parliamentary democratic republic does not have a monarch, and the head of state is elected for a certain term. A parliamentary constitutional monarchy has a monarch and is hereditary and has no term.

A constitutional monarchy, also known as a "limited monarchy", is a state system as opposed to an absolute monarchy. Under the premise of retaining the monarchy, constitutional monarchy establishes the sovereignty of the people, limits the power of the monarch, and realizes the republican ideal in affairs without adopting a republican form of government. It can be divided into a dual constitutional monarchy, a parliamentary constitutional monarchy.

Britain's "Glorious Revolution" set a precedent for a constitutional monarchy. Generally, the monarch is lifelong, the monarch is by definition higher than the other citizens of the country (this is a difference between the monarch and some other heads of state such as dictators), often the monarch belongs to a special class (nobility), and hereditary system is often a characteristic of the monarch.

Although the monarch is the head of state, the way in which the monarch is elected and the scope of his power will vary according to the system of each country. Even if it is the same country, the way in which the monarch is elected and the scope of his power are often different at different times. The constitutional monarchy is closely related to a country's national conditions and cultural traditions, and it has a certain degree of progress, but also a certain degree of compromise, backwardness, and limitations. Britain was first identified after the Revolution through the Bill of Rights.

The constitutional monarchy is one of the manifestations of the modern bourgeois representative system, the essence of which is that the bourgeoisie holds the legislative power through parliament, which is the most important state power. The parliamentary system in England is based on feudal legal documents such as the "Magna Carta of Liberty" and the "Oxford Statute" in the Middle Ages. The basic principles of "supremacy of law" and "limited royal power" established by them formed the political basis of British constitutional politics. The Glorious Revolution of 1688 was a "bloodless revolution", and the Bill of Rights was the constitutional text of a constitutional monarchy. The constitutional monarchy of modern Britain is characterized by the integration of monarchy, aristocracy and democracy on the basis of preserving the ancient constitutional tradition and establishing bourgeois political rule.

A democratic republic is another form of government in a capitalist state. This form sprouted in the 16th century, was formally established by the French bourgeois revolution at the end of the 18th century, and was accepted by most countries with a capitalist system for the next 200 years.

Under a democratic republic, the members of the organs of state power and the head of state are elected for a certain term. Due to the different relationship between the legislature and the executive, this system can be divided into a parliamentary republic and a presidential republic. In a parliamentary republic, the legislative power is vested in the parliament, the executive power is vested in the government, the government is headed by the prime minister and is accountable to the parliament, and the duties of the president are ceremonial and symbolic. In a presidential republic, the president is both the head of state and the head of government, and the president has both foreign and domestic powers. The President is elected at regular intervals and government ministers are appointed by the President. The President reports to Parliament, but does not have the power to dissolve Parliament. The President may exercise the right of veto on bills passed by Parliament. The United States, France, and other countries practice a presidential republic.

The general characteristics of modern democratic republics are: state power is at least formally vested in the majority, not one person or minority; The head of state is elected, not hereditary; The top state leadership positions are subject to a limited appointment system, not a tenure system, etc. Any political arrangement that possesses these characteristics can be classified as a democratic republic.