The American Civil War and World War One were different in how they defined American citizenship and the citizens' relationship with the war. Additionally, the US immediately began shaping peace efforts before both conflicts even ended.
The Civil War is still remembered by Americans today, while World War One is often forgotten. The main difference between the two wars is the way they defined what it meant to be an American and the citizen's relationship with the war, as well as the reason for fighting the war.
The defeat at the end of World War I led to a culture of resentment and blame in Germany, which manifested in ugly politics and a bankrupted country that couldn't participate in a European order. The United States, under Wilson, tried to shape the peace, crafting a new international order to prevent another global conflict.