Kaiser's offensive, French troops take German POWs, Kaiser observes battle

On July 13th, a surprise attack on the German line results in 27 prisoners. The Kaiser plans a major offensive, dreaming of a victory dinner in Paris. However, the French are forewarned and prepared, leading to a strategic retreat by the Germans. The Americans join the battle, marking a significant shift. The Kaiser realizes he will not achieve his dream of visiting Paris.

What was the significance of the Americans appearing in the front lines?

What realization did the Kaiser come to after descending from his observatory?