Policemen of the World
The world has changed a lot in the last century. In addition, with that, the world has become a different place in terms of the global theater and hoe countries interacted with each other. In this case, the situation developed where America is kind of the leader in world politics, at least militarily, and is in many ways “The Policemen of the World.” Consider things like the first gulf war, or America's actions in the cold war. it is not so much that these actions are necessarily justified, but it is the dynamic that has evolved politically in the last few years. it is something that causes a lot of problems, but some political theorists (funny how they are mostly American) that this is a necessary need for the current global political sphere.
The first thing is to realize that America is really involved in many geo-politics, and have sort of appointed themselves as the World Police. This involves many things. First, America is the only country with a sizable navy, and this navy is very involved with protecting ships in international waters from piracy. It also, for better or worse, fought to slow the spread of communism in the cold war. Weather this is a good thing depends on your opinion, but many countries under the control of the USSR suffered greatly in those regimes. The US also, due to economic interests, fights against the drug cartels in much of South America.
The reason this situation came about was mostly in the aftermath of World War 2. America had become a world power following the Battle of New Orleans in 1812, but really did not become the superpower it was in the Cold War until following the second World War. A lot of this was from the fact most of the countries in the world with strong economies had a lot of infrastructure damage from the war. America had a strong post war economy and a strong military that was not dismantled, so they became the natural successors for this role they see themselves in today. They also gained a lot of good will and soft political power with restructuring Europe and rebuilding it under the Marshall Plan. This idea of policing came along with the ideology of gambling that was paramount in their struggle with Russia. These factors, among others, are what put Americans with the role they find themselves today.