For decades, the official US position in times of war was neutrality. This is no different at the beginning of World War II. When Hitler came to power in 1933, most people knew war was on the horizon. The US Congress passed the first of many Neutrality Acts in 1935 which essentially made it a law NOT to become involved in any foreign war. However, America as not neutral. The Americans were actively involved in the war.
For over five years, the United States inched closer and closer to war. This can be seen in the many "alterations" to the neutrality position established by Congress.
Cash and Carry Policy (1937 - 1939) - when Germany invaded Poland in 1939, the allies (France and Britain) needed help. The Cash and Carry policy replaced the Neutrality Acts. The law stated that the allies could come to the US and purchase wartime goods in CASH but they must be CARRIED back to Europe on their own ships.
Lend-Lease (1941, March) - By 1941, Great Britain was the last independent nation in Europe and was heavily bombed by Germany. The Cash and Carry was altered to become the Lend-Lease Policy. It allowed the British to purchase weapons from the US on credit and the US would "lend" merchant ships to the British to transport those goods.
Atlantic Charter (1941, August) - British Prime Minister Winston Churchill and President Franklin Roosevelt met onboard Naval vessels off the coast of Canada (to maintain the illusion of neutrality). They, along with 26 other nations, agreed that the world could not survive if Germany and Japan won the war. The British and the Americans agreed to work together to defeat Germany. It was one step shy of a declaration of war.
Summary - although the US publicly announced their neutrality in 1935, the Americans were not neutral and it was only a matter of time before they entered the War.