Final answer:
The United States was able to successfully engage in world conflicts due to its immense industrial capacity, strategic diplomatic alliances, particularly with France, and its ability to mobilize vast resources leading to economic prosperity.
Step-by-step explanation:
Key Factors in American Success in World Wars
The question concerns the three key reasons why the United States was able to fight two major world powers successfully and win the war on both fronts. Firstly, industrial capacity played a critical role; the U.S. dwarfed Europe's great powers in production capabilities, ensuring a consistent supply of arms and essentials for soldiers.
Secondly, the importance of diplomatic alliances, like the one with France after the Battle of Saratoga, offered American troops vital support and turned what could be localized engagements into more globally influenced battles.
Lastly, America's ability to mobilize and integrate its vast resources, as evidenced by its economic prosperity during World War II, allowed it to not only supply the warfront but also to maintain and bolster domestic stability, directly translating into superior global power post-war.