I strongly believe it's the civil rights movement
Another way your question could be framed is “why do nations use imperialism on weaker countries?” and the simple answer is there are several motives such as ethnocentric purposes, religion, access to natural resources, expanding power, etc. Specifically people resort to imperialism on weaker countries because they are vulnerable to accept whatever helps the people survive in times of unrest.
After the War of 1812, America' sense of social and political unity was at an all time high, especially after fending off the British for the second time in less than 50 years. To describe this period of American unity, a Boston newspaper described this time of the "Era of Good Feelings." This title represented both the unity in America's moral after defeating the British, but it also refers to the lack of arguing/fighting in politics. This era brought the collapse of the Federalist party, with only the Democratic-Republican party remaining. This party began to unit and settle several differences that divided them prior to the war. This era lasted less than a decade and would precede some of the most divisive eras in American history.
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Answer: They are talking about life, liberty and the pursuit of happiness
Explanation: Hope it help
