Two party systems are most common in the English-speaking countries of the world.
A two-party system is a system of political parties that favors the appearance of two political coalitions (usually antagonistic in the political spectrum) to generate exclusion or positive discrimination of political minorities, happening in all the elections that one of them reaches the government of the nation and the other occupies the second place in the voting preferences, becoming the official opposition to the government. Its defenders argue that it generates political stability by excluding extremist sectors that could achieve parliamentary or presidential representation. On the contrary, its detractors argue that the fact that it excludes these minorities is undemocratic.
The United Kingdom had a clear two party system in its beginnings, with Conservatives and Liberals contesting power. Labourites soon emerged as a third political force. Little by little they gained in relevance to the point that in the last decades they have alternated in power with the Conservatives.
If the British is a system of classic monarchical bipartisanship because it respects and submits in the forms to the institution of the Crown, the American system is a typical example of presidential bipartisanship with republican essence. The evolution of the system has been to accentuate this bipartisanship, as more and more sums of money are needed to be able to do politics. Currently, there are only two major parties, known as the Democratic Party and the Republican Party, which have more than 90% support between them.