Me Thinks

As president Monroe had the final say in  Responding to the Alliances plan to invade South America to retake the countries that had gained there independence from there mother countries. The US reacted by stating that "we could not view any interposition for the purpose of oppressing them, or controlling in any other manner their destiny, by any European power in any other light than as the manifestation of an unfriendly disposition toward the United States." The United States basically said that they would not stand by and watch while other countries that fought for their freedom get slaughtered. If the Quintuple Alliance was planning to take back their colonies in South America then they were going to have to deal with the United States. They would also have to fight Britain because they supported the idea that no European power should have colonies in the Western hemisphere.

The Quintuple Alliance was a force to be feared by every country on earth. That's why Monroe's response was so jaw dropping.  This statement made them realize that the US was not a country to mess with and that they will lose a lot more than they gain if they fight the United States and Britain. The South American countries that had won there independence were grateful and surprised that the US and Britain stood up for them against the Quintuple Alliance.