World War I was not as consequential for the US as World War II, but it was important nonetheless.  Among its effects were:

• It made the US more of an important world power.  The fact that US participation swung the outcome of the war helped make the US a first rate power after the war.
• It also pushed the US towards isolationism.  Many Americans felt that the war had been unnecessary and did not want to get involved with further foreign wars.
• It helped lead to intolerance in the US.  This happened both during and after the war.  During the war, propaganda helped create animosity towards Germans.  After the war, there was a “red scare” that came about in part because of the war.
• It helped bring African Americans to the North.  African Americans moved north to work in factories making war materiel.  This started to change the African American experience.

What were the consequences of World War I?

The major consequence of WWI was WWII.

After WWI, the Allied Powers imposed the Treaty of Versailles on Germany.  This treaty humiliated Germany and made Germans very angry.  It did this by, for example, taking away German territory and preventing Germany from having a strong military.  It also weakened Germany by making Germany pay huge reparations to the Allies for the costs of the war.

As Germany was weakened and humiliated, Germans wanted in some way to get back to what they saw as their rightful status as a great country.  This led them to support Hitler and his Nazi Party.  Hitler's attempts to regain lost power (and then some) led to WWI.

Without WWI and the Treaty of Versailles, WWII would not have happened, at least not in the way that it did.