Why did the United States enter World War I?

The United
States entered(1914€“1918) despite a long history of isolationism. Since its inception, America
had stayed out of European wars, so why did it enter WWI in 1917? There are three reasonsone
primary and two secondarywhy the US joined the conflict: Germany's unrestricted submarine
warfare, the Zimmermann Telegram, and President Woodrow Wilson's idealism.

After the commencement of hostilities in 1914, America attempted to trade with both
sides. But the British had other ideas. Britain had the world's most powerful navy, and they
blockaded Germany. Germany responded to this threat with submarine warfare. Because of the
British blockade, American trade with the Allies increased as its commerce with Germany shrunk.
In 1915, the Germans sank the Lusitania, killing over one thousand
civilians. The Lusitania was a passenger ship that was carrying ammunition
for the Allies. In fact, Germany had warned civilians not to travel on ships carrying weapons.
In...