The main result was the treaty of Versailles with Germany laid the guilt for the war on " the aggression of Germany and their allies."
The League of Nations oversaw the argument and made a solution to prevent another war. However, the United States Congress believed it was best for countries to self-govern themselves, so it did not join the League of Nations.
At the end of World War I, the economy was was strong, and believed it would continue to grow if they built from within. This thinking, ultimately lead to Isolationism: the belief that if countries only focus on their own issues, no world problems will happen.
Unfortunately, the Isolationism, preached by the United States, lead to the start of WWII, where the United States were forced to exit their Isolation due to their size and power.