The answer is it made foreign policy. The Monroe Doctrine was a US policy of contrasting European colonialism in The Americas starting in 1823. It specified that additional efforts by European states to take govern of any self-governing state in North or South America would be watched as "the appearance of an unfavorable disposition toward the United States."
On December 2nd, in 1823, President James Monroe presented what was going to be known as the "Monroe Doctrine". The doctrine had 4 main points: the European powers could no longer form new colonies in any Latin American countries. The United States would see as a direct attack if any nation would intent to colonize a Latin American country. The United States was not going to interfere any longer in any internal conflict occurring between European countries. And lastly, the United States recognize and would not interfere in any colony or independent nation in the Western Hemisphere. The Monroe doctrine put the United States as the "Big Brother" of the American continent, putting themselves as the ones in charge for protecting all the other countries, specially the Latin American ones. But this also invoke the U.S sympathy for revolutionary governments, in South America specially, because the United States had stated that they would not interfere in any independent country, so by supporting revolutionary governments, the country had a way of hold some sort of influence on South America without formally violating the principles of the Monroe Doctrine.
