Geography is probably one of the most important things that influence a country’s government outside of the people themselves.
For example: the size of a country influences whether or not a country will have a federal or unitary government system. Countries that are physically quite large i.e. Brazil or the USA are a lot more likely to have federal forms of government because the size of said countries means that people at one end (likely but not necessarily due to geography) are going to have very different problems that people at the other end and are thus going to need very different solutions to their problems.
Government also plays an important role of determining the priorities of a government. For example if a country is located next to a fault line e.g. Japan or a place where volcanoes are present e.g. Italy the a government is going to have to take into account what will happen when an earthquake or volcanic eruption happens and make emergency response plans to deal with them and make sure their people stay safe.
Thus geography helps influence a country's government.
Hope it was helpful!!