Answer:
B.Roosevelt is warning isolationists that American democracy will collapse if Germany wins the war.
Explanation:
The importance of this speech by Roosevelt lays on the reality that Germany was winning the war, but many americans shielded on the "Isolationism" were trying to keep America out of the war and leave Europe alone, they defended the idea because of the long shot that it would be for Germany to actually invade America, but there were already several actions taken by Germany in other states, like Norway, and they were trying to conquer the world, so American democracy was at risk if Germany were to win the war.