There are various types of government unitary federal confederal and each of these has different examples and can be seen in different parts of the world. Unitary governments are those where the power all lies in the middle, with the state and it is quite opposite to the concept of democracy (for the people, by the people). The USSR had a unitary government. A federal form of government is one where the center (the government) only has power over some matters such as defense and foreign policy. In the confederal form of government where common action related to some units are concerned, these are to be decided by the states and a treaty may be drawn up for this purpose.
Different types of countries have different types of government unitary federal confederal because of the fact that as times have gone on that is how things have changed in these countries. Certain countries that initially had unitary forms of government have now adapted the federal form of government due to certain events in history. The UK initially had a unitary form of government where all the power was with the monarch but today it has a federal form of government. Most colonies had a unitary form of government where the power was with the colonizer.
Even today certain types of government unitary federal confederal do exist but certain modifications may have been made to make the system more liberal. By way of example, though the UK now has a federal form of government, the Queen still has to sign Bills that the Parliament passes so that they can be considered to be Acts and become part of law. Though by convention (which is general practices that influence the political system of the UK) the Queen cannot say no and has to approve bills but this could change in the future if the need to do so is felt.
If you want to get an example of confederal forms of government of the various types of government unitary federal confederal, the European Union is classic example. The Union itself has several countries in it but some matters are decided by all the countries together such as trade, currency, laws and such like. These have to then be implemented in the various countries that make the European Union and this is done via treaties and agreements between the countries at a central level. Hence, within the Union you see a confederal form of government while in the states that make the Union you will see a federal form of government mostly.
Though countries in the west now have federal forms of government, countries in the east do still have unitary forms of government the types of government unitary federal confederal. Iraq had a unitary form of government under Saddam Hussein. Pakistan had a unitary form of government under Colonel Pervaiz Ashraf from 2000-2008 and so as you can see it is not as if any of the types of government unitary federal confederal doesn’t exist anymore.