Trying to explain how the rise of the United States of America happened before, during and after the Cold War is like talking about the birth of Superman. It is amazing how they conceived a super nation, with super powers, known better as hegemonic powers.
Sorry if I started with a Hollywood character comparison, but it is the best way I found to explain how I understand the development of our northern neighbor. However, is not so easy as that.
Since colonization, the citizens of that part of North America were very worried about their own definition. We have to keep in mind that the country was founded by immigrants that were looking for a better place to live, far away from the hard hands of the British government.