What caused people to believe America could win the war?

People believed America could win the war due to a combination of factors, including the nation's industrial capacity, which allowed for rapid production of war materials, and the motivation of its citizens to support the war effort. Additionally, early successes in battles and the involvement of allied nations provided a sense of optimism. The belief in democratic ideals and the moral imperative to fight against tyranny also fueled confidence in a victorious outcome.