The United Kingdom of Great Britain and Northern Ireland has no written constitution. The two main branches of the English constitution are: (A) the legislative power which is the power of making, altering or repealing the laws; and (B) the executive power which belongs to the Parliament. On the other hand, the constitution consists of elements such as: status that is laws made by the Parliament, important court cases and established practices.
While the British constitution consists of two branches, as shown above, and the Queen as the Head of State who represents the people (but the real power lies in the Parliament), the United States and Romanian constitutions consists of three fundamental state powers: the Executive Power, the Legislative Power and the Judicial Power.
In the United States the three powers are represented, in order with above, by: the President, the Congress, the system of Courts. In Romania the Executive Power is held by the President and the Government which is lead by the Prime Minister, the Legislative Power is held by the Parliament and the Judicial Power is represented thru the Courts.
In the United Kingdom the Parliament is the most important part of the state power. A full duration of it is seven years. No bill can become law until it has been sanctioned or "read" three times by both houses and has finally received the royal assent, which practically never refused any measures that have passed both Houses of Parliament. The parliament consists of two houses: the House of Commoners (the Lower House) which is made up of 650 members, who each represent a constituency; and the House of Lords (the Upper Court) which consists of around 1200 members. Only the Queen can provoque, prorogue or dissolve the Parliament. The members of the House of Commoners win their seats in the Parliament by a majority vote. The leader of the party which has the most seats in the house of Commoners becomes Prime Minister. He than chooses the members of his cabinet, called the ministers. General elections are held every five years although the Prime Minister may call one earlier.
The United States Congress is made up of two houses: the Senate to which each state elects two senators for a period of six years; the House of Representatives where each state elects a certain number of representatives in direct proportion with the population in that state. They are elected for a term of three years. Bills can't become law unless they have been passed by 2/3 majority of each house, and if there are passed by both houses. But in case a bill doesn't pass thru both houses the President can veto it.
In Romania the Parliament consists also of two houses, named exactly as in the United States. The senators and representatives are elected thru universal, direct, equal, secret and freely spoken vote. A difference from America's Congress is that the nr of senators and representatives are set by a special type of organic law called Election Law. The President can also dissolve the parliament, only after consulting the Speakers of the two Houses and the leaders of the main political parties in the Parliament. But he can only do this if the Parliament hasn't given its "Trust Vote" for the naming of the Government in 60 days from the first time it was called and also after rejecting two calls for a naming.
We can only speak of a President in US's and Romanian cases. The big difference between the two countries in this matter are, first of all in the United States the president has real political power; second matter is that in Romania the presidential term is five years, while in the States it's only four years. And third difference is that the United States Presidential Candidates are chosen by the political parties either through Primaries or Caucuses. One major difference between America and us is the election of the Vice-President.
The Romanian President names the Prime Minister and the Government, but only after a Parliaments "Trust Vote". In the United States the President names his Cabinet with the approval of the Senate only. The members of the Cabinet are the President's advisors and they help him in carrying out his policies and duties. Their term is usually a full four years. They are responsible to the President for their official acts and the Congress has no power to remove them.
The United States President can be judged whether he has, or not, acted constitutionally by the Supreme Court. If the Federal Judges consider that the president's behaviour was indeed unconstitutional he may be impeached (that is accusing him of a crime against the state). In Romania the parliament in a general reunion of the two Houses can decide, with at least 2/3 of the votes, to place the president under the accusation of high treason. The final decision lies with the High Court of Justice.
A unique feature in the Romanian Legal System represents the Constitutional Court. Its main functions are to say whether or not a law confirms with the Constitution, whether international agreements are from the Romanian Constitution point of view constitutional, whether the Parliament's acts are according to the Constitution, it watches over the Presidential elections and confirms the result, decides whether a political party is or not constitutional, etc. The Constitutional Court is made up of nine judges, three named by the president, three by the House of Representatives and three by the Senate, all for a term of nine years. They chose from among them a Chairman for a term of three years.
In the United States the Supreme Court has the power to judge a law passed by the Congress or the President and decide whether it is according to the Constitution. In other words it interprets and repeals a good many laws passed by the Congress or the President by declaring them unconstitutionally.
The United States system of Governing is a centralized one.