What pulled the US into WWI? List and explain several reasons the US joined the war.

Main reasons why United States were the sinking of many ships by the German submarines, including the sinking of Lusitania, a ship that carried many citizens of United States. On the other side, another important cause was the Zimmerman affair, named after German politician Zimmerman, who send a telegraph to Mexican leaders to urge them to enter in war on their side against Germany.

Explanation:

Although United States entered the war in 1917 they supported the cause of Allies even before they officially entered the war.

Still, Congress wasn't supportive of the idea that United States enter the war. But when this affairs came into light, it was impossible to stay out of war any more.

After US entered the war the outcome of the war was decided.