The United States of America and Great Britain have a lot of in common but the same times have a number of differences. The electoral systems of the UK and the US differ a lot. The United Kingdom uses different electoral systems and among them we could mention. First Past the Post, which is used for the whole national elections and also when the local government is elected in England and Wales (earlier it was used in Scotland too).
Additional Member System was invented after submission of the regional devolution in 1999 for the Scottish Parliament, Welsh meeting and London meeting. It is rather modern invention, which was undertaken after electoral system reform.
Single Transferable Vote system is used for the election into the Assembly of the Northern Ireland and also is used for the Local administration. Party Lists are used for the elections to the European Parliament and that is also rather modern invention and applied as the UK is the member of the European Union.
And finally, Supplementary Vote, is used for the mayors election in the different cities, for example London. We see that the electoral system of the United Kingdom is rather complicated and strongly depends on the territorial division of the country. It should be noted that the United States is also dependent on the territorial division and each state has its constitutional and the elections to the local governmental organs are held due the legislation of the each state. But if we speak about electoral system globally we should mention about the Primaries, which are used for the President elections. This the first type of the election, when one candidate from the party is elected. Between the chosen candidates the general election is held and the core idea of the Primaries is in the fact that candidates from different parties should not take the votes of each other on the main elections, as their electorate is quite the same target group. Sometimes those who have lost the primaries took part in the president elections, but as independent candidates, without support of their party. Primaries could be opened, when everyone could take part in the elections and closed, when the members of the party, holding the primaries, could vote. The Primaries are the core peculiarity of the United States electoral system. It should be noted that a number of states refused from primary use of the Primaries. The different system are used for counting the votes and different schemes. A number of southern states have a tradition to support the candidate, which would take the arithmetic majority of the votes. In southern states the break between the winner and the nearest competitors.
It should be noted that the both systems differ a lot and the United Kingdom has developed the electoral systems suitable for their political structure and the United States for theirs. I think that the core role in the difference between these states is that they have different political structure and this causes so severe difference in their electoral structure.