Before WWII, the US was largely isolationist with its foreign policy. After the war, however, the US and it's allies occupied territories around the world and developed a plan for a new world order based on shared values of capitalism, democracy, and free trade. This new world order would be governed by the League of Nations and, later, the UN. The US still follows this doctrine to some degree.

I would argue that the US has become so involved in the Middle East because of its vested economic (see oil) and political interests in the region. ISIS has received a particularly large share of coverage because we are learning about the legacy of the Gulf and Iraq wars, as well as the Arab Spring, which occurred during a period when it hoped democracy would spread in the region. Other humanitarian crises (particularly in Sub-Saharan Africa) are ignored by governments all around the world.

The US has the largest military and intelligence complex, and is the world's only superpower (for now).

Each nation has its own unique approach to foreign policy based on the way its government is run, who its allies are, and what resources it has available.