When the U.S. Constitution was being drafted, its writers had the British Parliamentary system to base on. The British system was the system they were used to and had learnt since childhood. However, because the monarchy was one of the main things that the former colonists had rebelled against, any form of monarchy and most forms of concentrated power were avoided.
The most fundamental difference between the political system in the U.K and the U.S is the constitution. The United States has a written constitution which is very difficult to change. The UK does not have a single document called the constitution but instead its constitutional provisions are scattered over various Acts of Parliament, any of which can be changed by a simple majority in the Parliament.
Both the U.S. and British political systems have a head of state, a court system and an upper and lower house. The U.S political system has a constitution which lays out the rules for government and the rights of the people, however, the U.K has documents with constitutional provisions which lay out the same rules. Both systems are democratic in nature, as governments are put in place and removed from power by the will of the people and both have systems of checks and balances to limit the power of any one branch.
Head of State
In the U.S. political system, the president is the official head of state. The president is elected under the electoral college system. In the U.K., although the prime minister usually has the spotlight on political matters and is the official head of government, the queen or king is the official head of state. The queen officially signs off on acts of parliament and, just as the U.S. president delivers the State of the Union Address every year, the queen reads the "Speech from the Throne," which is written by the prime minister. In U.K, the monarch is more of a...