Read this excerpt from Franklin D. Roosevelt's "Four Freedoms" speech. Which part shows his purpose in making the speech to Congress? During sixteen long months this assault has blotted out the whole pattern of democratic life in an appalling number of independent nations,
great and small. The assailants are still on the march, threatening other nations, great and small.
Therefore, as your President, performing my constitutional duty to "give to the Congress information of the state of the Union," I find it,
unhappily, necessary to report that the future and the safety of our country and of our democracy are overwhelmingly involved in events far
beyond our borders.
Armed defense of democratic existence is now being gallantly waged in four continents. If that defense fails, all the population and all the
resources of Europe, Asia, Africa and Australasia will be dominated by the conquerors. Let us remember that the total of those populations and
their resources in those four continents greatly exceeds the sum total of the population and the resources of the whole of the Western
Hemisphere-many times over.
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During sixteen long months this assault has blotted out the whole pattern of democratic life in an appalling number of independent nations, great and small. The assailants are still on the march, threatening other nations, great and small. Therefore, as your President, performing my constitutional duty to "give to the Congress information of the state of the Union," I find it, unhappily, necessary to report that the future and the safety of our country and of our democracy are overwhelmingly involved in events far beyond our borders. Armed defense of democratic existence is now being gallantly waged in four continents. If that defense fails, all the population and all the resources of Europe, Asia, Africa and Australasia will be dominated by the conquerors. Let us remember that the total of those populations and their resources in those four continents greatly exceeds the sum total of the population and the resources of the whole of the Western Hemisphere-many times over.

Explanation:

For a little context, FDR wanted to counter the tendency of Americans to avoid any involvement in affairs beyond their borders and their isolationist policies.

I hope this answers your question :)