How did the monroe doctrine, social darwinism, imperialism, and manifest destiny played a role in shaping american foreign policy in the 19th and 20th centuries?

The Monroe doctrine was manifested through the idea that no foreign powers from Europe should invade any American Countries, which was seen when the US supported any colony that wanted to free itself from its colonizer. Imperialism was important because countries started spreading and colonizing Africa and Asia and the US even participated with its Manifest Destiny and the Philippine campaign. Social Darwinism was seen in the time of the great depression before FDR became president because only the strongest members of the society would survive while the poor would just be abandoned.