1. How did the Great War change America (USA) internally?

This was also the first time the US government agreed to send large numbers of American soldiers to war across the sea.
In the beginning, the US didn't have a drafting policy. It was in May 1917, the Congress passed the Selective Service Act. This act requried all men from ages 21-30 to register for military service. Before this Act, military service was something one can volunteer to do. But after this act, military service was mandatory. In order to encourage the Americans to enlist in the Army, propaganda campaigns were launched.


2. How did the Great War change the way war was fought, in general?

Advance technologies completely changed the way wars are fought. Technologies like machine guns and heavy artillery changed the war. Machine guns can fire an amazing 600 bullets per minute. Instead of firing from a tiny pistol, a soldier can fire a .30 cal at a group of enemies without worrying about getting killed. Strategies were also changed. Instead of attacking or defending heads on, well grouped machine gunners can effectively defend a large force.
"Big guns" were also a new weapon introduced. These "Big guns" are able to punch 2100 pound shells. These guns scared the hell out of the enemies from far away.
These faster and deadlier weapons prevented wars from being fought on plains. Soldiers from each side had to dig trenches to prevent sharpshooters from hitting soldiers. Chemical weapons were also introduced into the war. The Germans were the first to use chemical weapons against its enemies.
Technologies like tanks were invented. The Allied took this opportunity to develop tanks. Then they used tanks to run across the no-man's land and attacked the Central Power.
Other inventions like improved planes and ships changed how wars are fought. Germans developed U-boats that can go underwater and go undetected to the enemy ship.