Answer:
Russia
Step-by-step explanation:
The Monroe doctrine was made in prevention of the direct intervention/involvement in affairs in the Northwest region of American by the Europeans . the Monroe doctrine mentioned Europe's intervention but Didn't mention the Soviet Union which was partly Europe and Asia as at that time.
The Americans were also concerned about the spreading of communism in this region and the father and held of all communist communities then was the soviet union. therefore the Monroe Administration had concerns about Russia ( soviet union ) intervention in the Northwest region of America.but didn't mention then in the Monroe doctrine.