If you look at the U.S. now, what do you see? Well, what you do not see is this nation owning much of Latin America. In fact, there are 24 Latin American countries, and the U.S. controls only 1 out of those 24. The Monroe Doctrine did not allow the U.S. to dominate Latin America, if it really did help a lot, we would be in control of many more countries.
The Monroe Doctrine was a policy written by the U.S. in 1823, it stated that efforts by European nations to colonize land or interfere with the states or countries in North or South America would be seen as acts of aggression, requiring U.S. intervention. It also said that the U.S. would not interfere with existing European colonies, nor meddle in the internal concerns of European countries.
Now, this stated that the U.S. would not meddle in internal concerns of European nations. So, say Paraguay had a rebellion against France, the Monroe Doctrine would not allow the U.S. to help in anyway. How would that help the U.S. dominate Latin America, if they could not defend a country and possibly control that country?
The Monroe Doctrine also stated that the United States would not interfere with existing European nations. All of the land in Latin America was already conquered by people, and were established countries. This means that if the U.S. followed the guidelines of the Monroe Doctrine, they could not mess with all of those countries. What does that leave the U.S.? There is no more land for them to dominate.
Did the U.S. follow this set of instructions when Cuba rebelled against Spain? The answer to that is no, no they did not. So, why would the other European Nations, take the Monroe Doctrine seriously, and follow its guidelines? There is an example of this when British and Venezuela had a border dispute. The Secretary of state sent a note to Britain informing them that their actions were trespassing the Monroe Doctrine. They