Here’s a snapshot of U.S. public opinion after Europe had been at war for almost a year, from the July 29, 1940, issue of Life Magazine. (You can view a larger image by clicking the image above.)
56% of the American population thought that German and Italy were going to win the war, and two thirds believed that the United States would be in danger if that happened. Over 70% believed that the U.S. should immediately begin compulsory military training for all young men.
If Germany and Italy were to win the war, then an overwhelming 88% of the public believed that the U.S. should arm to the teeth at any expense.
American supported the Monroe Doctrine, and was asked whether the U.S. should defend the hemisphere against foreign invasion. 80% believed that Canada should be defended, and almost 75% believed that Mexico and Central America should be defended. Two-thirds believed that South America and the West Indies should be defended, and 58% believed the same with respect to Greenland.
If America were ever to get into a predicament such as Belgium, Norway, or Finland and was apparently being beaten, a majority believed that America should continue to fight at all costs, with only a third advocating surrender to prevent further bloodshed and destruction.
Overall, 43% of Americans were optimistic as to the future of civilization, with 35% pessimistic, and 20% not knowing.