How is american entry into second world war best explained?

I know that there were many factors which triggered american decision to enter the war, but which one is the main. How can the american decision to entry the second world war be best explained?

The attack on Pearl Harbor on December 7, 1941 was certainly the immediate cause of the US entering WWII. Many historians argue that US foreign policy prior to that attack led the Japanese to conclude that a preemptive strike against the US Pacific Fleet was the only way to gain the upper hand in what appeared to be an inevitable struggle with the US. The declaration of war on the US by Germany a few days after Pearl Harbor solved FDR's dilemma regarding how to fight the most immediate threat (in his view)--Nazi Germany.

Its been stated by many historians that the US embargo on Japan, and numerous tactics to antagonize them led to the strike on Pearl Harbor. This attack was not a surprise. Prior to this the US had been supplying England with weaponry and pilots. The powers within the military industrial complex including FDR wanted a war with Japan and Germany but the population was, for the most part against it. They believed that an attack on the US would rally popular support for the war. The Japanese fleet was tracked by experimental radar systems on route to Pearl Harbour. The plan was to warn the fleet just prior to the attack so it could be repelled, and the large carriers were removed from port to avoid there loss, but the message of the impending attack was delayed and the Japanese caught the US naval base by surprise.

The immediate cause of US entry into WW2 was Pearl Harbor. However, FDR knew perfectly well that the US would eventually have to become involved. He knew (or had a good feeling) that the Japanese would attack the US but never imagined that it would be in Pearl Harbor and that it would nearly destroy the Pacific Fleet.

When Japan attacked Pearl Harbor that pushed the USA right into the war, But also we have been helping England fight off Germany with supplies and the German subs kept sinking American Ships so we got real close to declare war on Germany but Japan pushed us right into it.

we were forced to enter the second world war because of japan bombing pearl harbor. them trying to take out a big part of our navy made it so we had no choice to.