* The memory of World War I: The US had fought in World War I and many Americans had died. They did not want to see the US get involved in another war in Europe.
* The Great Depression: The US was in the midst of the Great Depression, and many Americans were struggling to make ends meet. They did not want to see the US spend money on a war in Europe when there were so many problems at home.
* The belief that the US was safe from attack: Many Americans believed that the Atlantic and Pacific Oceans were too wide for any country to attack the US. They did not think that the US was in any danger from Germany or Japan.
* The rise of fascism in Europe: Some Americans were sympathetic to the fascist regimes in Germany and Italy. They did not want to see the US fight against these regimes.
* The neutrality acts: In the 1930s, the US Congress passed a series of neutrality acts that made it difficult for the US to get involved in a foreign war. These acts prohibited the US from selling weapons to belligerent countries, and they also made it difficult for Americans to travel to Europe or Asia.
These factors all reinforced isolationist sentiments in the US, and they made it difficult for President Franklin Roosevelt to convince Congress to declare war on Germany and Japan. It was not until the attack on Pearl Harbor in December 1941 that the US finally entered World War II.