Since the end of World War I, the United States has returned to its traditional foreign policy of both withdrawing from conflicts overseas and maintaining a moderately tight military program. By September 1939, this "isolationism" was supported by strict legislation that prevented the U.S. government or private organizations from selling weapons or providing loans to any country in the war. Most Americans condemned Germany's war and hoped Britain and France would win the war, but they knew all too well that the United States would just stand idly by. During President Roosevelt's administration, american society underwent some changes. Americans generally recognize the nature of nazi regime and Japanese militarism, and that they will ultimately pose a great threat to American interests.
But Roosevelt did not want to be involved in war, so his policy was to help the European allies, to remain within the framework of "all other ways other than war", while being tough enough against the Japanese, but not wanting to provoke Japan and form a grudge with Japan. The details of this policy changed over time, but its general principles remained until December 1941.
In fact, the United States was not completely neutral, and when the "Cash and Cash" Act was successfully passed in November 1939, the countries participating in the war used cash to buy a large amount of U.S. weapons and equipment, on the condition that they transported them back home in their own ships. The geographical realities and Britain's strong naval prowess meant that this would benefit the Allied side, which was the original intention. This was enough to ensure that the Anglo-French coalition had hopes of victory, but it was dashed after the French surrender in June 1940. The U.S. rearmament program was immediately on the agenda, especially after the signing of the Two Oceans Naval Act in July, which led to a significant expansion of the U.S. Naval Force. The purpose of this bill is still to guard against the German threat, but it also makes the Japanese government worried.
It would take a few years to build those ships, and if that time came, the terrified Japanese would no longer be able to match them unless they were stronger. So then, in the fall of 1940, the U.S. government introduced the Conscription Act, which established the conscription system for the first time in The history of the United States, but the United States had not yet officially entered the war. But Roosevelt, if he continued to help Britain, could pose some incalculable dangers, because sending weapons and equipment to Britain might, in a sense, be so that Hillert could use them for free after winning the war.
But then a new problem arose, namely that Britain's cash was about to run out, and it was very likely that there would be no way to continue the war, let alone the ability to pay for American goods. The solution later developed was the so-called "lend-lease" scheme, which was implemented in March 1941. Britain, and later other allies, including the Soviet Union, received large quantities of weapons and other strategic supplies from the United States. However, the production cost of these materials was first paid by the US government, and then returned with interest after the war.
In fact, Roosevelt knew that it was not enough to produce weapons for the British, because the Germans would sink them as they passed through the Atlantic. Thus, in 1941, the U.S. Navy played a proactive role in the battle against German U-boats in the Great Western Sea. But to what extent this action will extend is unclear to Americans. By the fall, American warships in the Atlantic were doing the same thing as the British and Canadians. Although everyone knows in their hearts, Americans still do not want to participate in the war head-on, and deliberately want to avoid it.
In August 1941, the Conscription Act was simply renewed in a vote in the United States Congress. After all this, Hitler became vigilant, but he was content to fight against his existing enemies. Incredibly, four days after the Pearl Harbor attack, he changed his mind and declared war on the United States, a decision that left Hitler's regime doomed to the final defeat and, like Japan, could not escape a total collapse.