Roosevelt's corollary was adapted from the Monroe Doctrine to protect unstable Latin American nations from being controlled by the European nations they owed money to. But it was soon
extended to protect:

multinational US corporations

overseas military troops returning to the US.

diplomatic corps serving in Europe.

foreign workers in the US.

multinational US corporations

Explanation:

Roosevelt declared the United States' intention to make effective use of its newly acquired naval force to preserve peace in America, and to ensure the free exchange and financing on terms of the United States, in the same way as achieved by European powers worldwide.  Roosevelt decided to avoid any justification from the European powers to interfere in Latin America as it would endanger interests and security of the U.S. The involvement of the US kept going through loans, the import-export activities, the existence of American businesses in Latin America, extended to protect the self-interest of the U.S.

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