The United States became involved in the second world war while it was supporting our allies borne of the first world war. We declared war on Japan after that country, while seeking our neutrality in diplomatic channels secretly planned and attacked our ports in Hawaii. Hawaii was a protectorate of ours and not a state at the time. Japan and Germany had signed an agreement (pact) to support each other against what they thought was a meddlesome nonaligned country. We had lost thousands of cargo tonnage on the open sea due to the sinking of our ships by German U-boats (submarines), while only trying to continue supporting Great Britain against the axis powers of Japan and Germany.
1939 for europe, 1941 for the us
At America, in order to start a fake war.
Europe
Franklin Roosevelt was the US president when WW II began in Europe.
Europe
the cold war
Poland
The US felt Europe should handle Europe's problem.
People in the US felt that Europe was Europe's problem.
People in the US knew that there was a war going on in Europe; and a war going on in Asia. And most of the adults had lived through this scene before, only 20 years earlier when there was a war in Europe, called the "Great War." And greatly had no sympathy for Europe which seemed to start "problems", let it get out of hand, then start asking for the US to bail them out of the trouble. In the US it was sometimes referred to as "isolationism." Then, in the late 1930's, it was happening again. When WW2 began for the US on December 7, 1941; the "Great War" had to be re-labled WW1, so World War 2 could be called World War 2. And yes, the US bailed the Europeans out of the fire, for the second time in the span of only 20 years.
The United States did adopt at the beginning of the war in Europe a policy of neutrality.
The Allied Armies landed back in Europe to start the end of the war.