Seeing that you are operating from a textbook and an instructor's class, I would suggest that everything you get from here should be checked against these particular sources.  In general, the role of the United States in other nations' affairs was primarily driven by the fear of Communism.  At the time of the Cold War, and especially prevalent in the 1950s and 1960s was the belief in the domino theory.  This idea was that if one nation in a particular region "went Communist," in a matter of time all of the nations in that area would follow suit.  This theory ended up committing the United States to intervene in any region where the threat of Communism was perceived.  Coupled with the Soviet Union's desire to force a challenge to the United States away from its own soil, such a theory ended up driving much of the US foreign policy at this time.

The topics that are the focus of your paper seem to take US history from the time of early imperialism under Teddy Roosevelt in the first decade of the 1900s to the time when the Cold War was beginning to heat up in the late 1940s and early 1950s.

So with those two larger topics in mind - imperialism and the Cold War, you may want to talk about the development of the first:

* how the United States became an empire and expanded its territories to include the Panama Canal, control over the Caribbean, with heavy influence over Latin America and the Philippines.  Include why the US would do this - for world power in competition with other empires, and for control of resources which would aid our economy

And the beginning of the Cold War second:

*how our goal of expanding our control as an empire changed into a foreign policy of containing the Soviet empire's expansion, and controlling more resources and influencing other countries with economic and military aid so they wouldn't be communist, or so the Soviet Union would not gain access to their resources.

In general, the US involved itself in the affairs of other countries quite a bit during the Cold War.  But if you are only supposed to be talking about the Cold War, only the Truman Doctrine, Marshall Plan, and Korea (I don't have your book so I don't know about the map) pertain to your question.

The Truman Doctrine and the Marshall Plan showed that the US would give economic aid to countries to try to stop communism.  The Truman Doctrine and Korea showed that we were willing to resort to force to contain communism as well.

You might want also to talk about the overthrows of governments in Iran and Guatemala in the early 1950s.