What was the immediate cause of American entry into World War 2?

Answer 1

Japan bombing Pearl Harbor on December 7, 1941.
The Japanese attack on Pearl Harbor, December 7,1941 was the immediate cause of the United States entering WWII. The US declared war on Japan after the attack, and two days later Germany declared war on the US and we were in it.

Answer 2

The Japanese attacks on the US at several places in the Pacific & Asia: Philippines, Wake Island, Guam, Midway Atoll, and the Hawaiian Islands. The Japanese attack against the US Military bases on the Hawaiian island of Oahu is often called the "Pearl Harbor attack", although the attack was made against several US bases in addition to Pearl Harbor. The Hawaiian attacks on Sunday morning, December 7, 1941 occurred a few ours before the other attacks. For those places west of the International Date Line, it was December 8, 1941.

Answer 3

The immediate cause was the Japanese bombing of Pearl Harbor, Hawaii. However FDR had been trying to gently nudge public opinion in that direction since the fall of France in 1940. However this only got us into the war against Japan in the Pacific, there was a significant proNazi minority of very influential people in the country (e.g. Henry Ford) that would still have opposed entering the war in Europe.

However Adolf Hitler made a serious strategic error and personally declared Germany to be at war against the U.S. (in support of Japan). This act caused the U.S. entry into the war in Europe.

Answer 4

Pearl Harbor.