The Monroe Doctrine was a policy of the United States which opposed colonialism in the Americas. The doctrine stated that efforts by European states to take control of an independent state in America would be considered an attack on the United States. The doctrine was implemented after almost all colonies of Spain and Portugal had achieved independence from the Portuguese and Spanish empires. One of the reasons why the Monroe Doctrine was so significant was because it allowed the United States to exert its influence over the New World undisturbed.
The United States, after sighing their Treaty with Panama, retained the right to defend the Panama Canal at any given time after the Canal was handed over to Panama.
