There is no single pin point event that caused the US to enter into WWI, but the Zimmerman Note was one. There was a message sent from Germany to Mexico asking for them to team up to fight the US. Britain intercepted it and shared new to the US. It was uncertain if it was actually true or if Britain made it up to get the US into the war, but that was one event.
Pearl HarborThere may have been other events, but the deciding event was the Japanese attacking Pearl Harbor.
The US was brought into World War 2 was the attack by Japan on Pearl Harbor, Hawaii. They had been helping England but had not officially declared war against Germany and Japan until after the Pearl Harbor bombing.
Both ships were the catalyst that brought the US into war. The sinking of the USS Maine brought us into the Spanish American War. And the Lusitania brought us into World War 1.
I really don't know
The Japanese
Franklin Delano Roosevelt and World War II brought us out of the Great Depression.
PEARL HARBOR
David Cameron
it was brought out by world war II, but most people want to think the war just made the depression worse.
The US Civil War and World War I.
Mexico
I really don't know