The US was attacked.
The final convincing event was the bombing of Pearl Harbor. After that, war was declared by the U.S., joining the European allies.
To help out other countries
America became involved in World War I due to a variety of reasons: the sinking of the Lusitania that led to American deaths, the publishing of the Zimmermann Telegram which promised Mexico some American territory, and their closeness with the Allies in World War I.
The US entered the war for a variety of reasons
Self defense, the US was attacked.
The immediate cause was Japan's attack on Pearl Harbor. This caused the US to declare war on Japan, which led to Germany and Italy declaring war on the US.
yes
John Pershing
they guns
pearl harbour
yes
The attack on Pearl Harbor.