Final answer:
Roosevelt anticipated that Germany and Japan could pose future problems for America due to their aggressive actions and expansionist policies. Germany was considered the greater threat in Europe, while Japan's aggression in Asia culminated in the Pearl Harbor attack, which led to U.S. entry into World War II.
Step-by-step explanation:
According to President Franklin Roosevelt, the two countries that might pose a problem to America in the early 1900s were Germany and Japan. Roosevelt's concerns were rooted in the aggressive actions of these nations: Germany being the greater threat to freedom in Europe, and Japan's expansionist moves in Asia, particularly the attack on Pearl Harbor. These concerns were reflected in Roosevelt's diplomatic efforts and the policies he endorsed, like the Roosevelt Corollary ensuring American intervention in the Western Hemisphere, and his actions to maintain a balance of power in Asia, demonstrated by his mediation in the Russo-Japanese War of 1904 which led to the Treaty of Portsmouth.
During the late 1930s, Roosevelt sought to support democracies at risk from the Axis powers by providing economic backing to nations like Great Britain and China. He intended to aid Britain and France against Germany through the strength of U.S. industry and implement a "Europe First" strategy prior to official U.S. involvement in World War II. The attack on Pearl Harbor by Japan solidified America's entry into the war, thereby confronting the problems posed by these two nations directly.