You seem to be giving a statement more than asking a question, but the period you describe ran from about 1815 to 1825, and is most closely associated with the presidency of James Monroe.
The phrase "Era of Good Feelings" was coined by a journalist, Benjamin Russell, in the Boston newspaper, <em>Columbian Centinel</em>, on July 12, 1817. Russell used that term to describe the new era taking shape, especially as Monroe's presidency began, after Monroe visited Boston as part of a goodwill tour of the US. President Monroe certainly went along with the description and was trying to evoke that "good feelings" sort of mood in the country. Historians see "The Era of Good Feelilngs" as having begun around 1815, after the War of 1812 and the end of Napoleon's wars in Europe, when the United States entered an era when it could focus on its own affairs and not need to be concerned about political and military happenings in Europe. The "Era of Good Feelings" is strongly associated with Monroe's two-term presidency, from 1817 to 1825. President Monroe made goodwill tours of the country in 1817 and 1819 to promote national pride and national unity.
C. Geek City Maker is the answer
The U.S. policy of containment was aimed to contain communism within its then current borders. The United states thought that communism was the ultimate evil because it did not allow its citizens any freedom and we wanted to stop its spread and influence. America then acted as a policing country during the Korean and Vietnam wars to try to prevent communism.
