The correct answer is the following.
Unfortunately, you did not specify to what war you are referring to,
It could be many wars: WWI, WWII, the American Civil War, the Revolutionary War, the War of 1812. You see.
Which one you are referring to?
However, trying to help you with something, we assume you are talking about World War I.
At first, the American people supported the idea of US President Woodrow Wilson to maintain a foreign policy of neutrality and no intervention in European affairs. However, after the interception of the Zimmerman telegram and the sinking of the Lusitania ship by the German Navy, President Wilson asked Congress for a declaration of war.
The message to the American people was that Germany was the enemy and peace and stability in the United States could be at risk if Germany won the war. So They had to be stopped for democracy to prevail.
That is why the US citizens thought it was a cause worth dying for. To protect America.
