Quite simply, the history of any country is tied inextricably to the geography of that country.  Would England have built the great and puissant navy that it did if it were the size of the United States?  Would England have colonized as it did if it had had room for its population on the island country that is smaller than the state of Illinois?  It is, indeed, dubious.

The countries which expanded their empires were all countries that had easy access to seas.  Russia, on the other hand, had only the Baltic Sea as its outlet; at one time Russia sold the rights to this sea to Sweden, so it became landbound.  As such, Russia remained in the Middle Ages until Peter the Great came to power and made great efforts to get the Russian people to progress.

On another point, the frontiers of a country have certainly influenced their histories, as well.  Belgium, that borders on France and the Netherlands and Germany, has been under the powers of all three countries.  Thus its culture and history has, undoubtedly, been influenced by its geography.

Those countries that have been part of the colonization of Europe are also affected by geography as their borders have been altered, depending upon the powers in control.  As mentioned in a previous post, the controversies over Israel's and Palestine's borders are results of interference by world powers (geopolitics).  In other countries of the Middle East such as Kuwait and Iraq, wars have occurred as a direct result of changes in geography.

It's important both because so many ideological disputes are land disputes (the Israeli-Palestinian conflict comes to mind here) and as a way of understanding the default relationships between nations.

Geopolitics, that is the relationship of physical territory to the established power structures is burgeoning field of political science. Beyond this, though, couching stories of conflict in a physical context is an important first step in "drilling down" into the marrow of understanding the positive/ negative realtionship between nations, as well as understanding national identity.

Whether people care to believe it or like it, and even for better or worse today the nations of the planet are connected. Therefore, across the board a general knowledge of the physical and political geographies are essential for the future of humanity...

I would say that it is important to understand these relationships so that you can understand why some of the political relationships are the way they are. The physical geography of a region has an affect on what natural resources are available to the country.

You can also think of this question in terms of the physical geography helping to determine the economics of a nation. If they country has a great deal of valuable natural resources and fertile farmland, it makes for a much different country than one that has a majority of its land as desert.

The physical geography and geographical relationships of countries are significant to not only understanding almost all conflicts that have taken place in the history of the world, but they also help us gain a better perspective of various cultures and political mentalities of those countries.

For example, one of the main reasons that Switzerland has been able to remain neutral through wars for decades is because of its geographic makeup.  Almost the entire country is surrounded by the Alps which allowed and still to some extent allows the Swiss to control who comes into the country.  They once controlled all the mountain passes and now have jurisdiction over many of the tunnels that they have built through the mountains.

The United Kingdom is in a similar situation.  As a group of islands, it has created a very distinct culture, and even though it is part of Europe by classification, its separation from the mainland has allowed it to better defend itself during times of war.

Afghanistan's geography is crucial to its history and current situation.  It is a country completely surrounded by other nations. For centuries, Afghanistan has been invaded by other nations hoping to control trade routes through it or to use its vastness and mountainous borders to become anonymous.

Physical geography is very important for understanding various things about countries and regions of the world.  For example, if you want to understand the possible impact of global warming, you have to know about physical geography.  You have to be able to know how much (and what parts) of a certain country would be flooded if the sea level rose, for example, one meter.

As far as the geographic relationship of countries goes, understanding that can help (to some degree) to understand the ways in which those countries will relate to one another.  For example, Russia's desire to have access to the Mediterranean through the Black Sea historically had a great impact on its relations with Turkey (or the Ottoman Empire) which controlled the passage between those two bodies of water.