What is the difference between the political systems in the United Kingdom and the United States?

The fundamental difference between the political systems in the UK and the US, is that the UK has a Parliamentary Monarchy and the US is a Federal Republic, which changes how the systems work and who they are lead by. In the UK, there is a heredetary monarch (the King/ Queen) who has limited powers and therefore executive and legislative powers reside in a Prime Minister and their Government. In the US, there are two Houses of legislature: Congress and the House of Representatives, to ensure a balance of powers, and the executive powers remain with the President. In the UK, the Constitution is not formally written in one place and is therefore uncodified, whereas in the US it is codified in one document which is constantly referred to in US political life.