That is true in the US, but that is not typical. I cannot think of another democracy that is as firmly two party as the US. Even the UK which I felt was too two party has always had some smaller parties (for many decades the Liberals, and then the Lib Dems, and Northern Irish parties), many smaller ones more recently (add the Scottish and Welsh Nationalists) and with two smaller parties gaining a lot of ground in the last few years the next general election looks like a four way fight.

In many countries multiple parties and coalition governments are the norm.