How did the war change the structures and roles of some nations?

The correct answer is D) the United States took on a new position as a world leader.

The war changed the structures and roles of some nations such as the US. The United States took on a new position as a world leader.

After the Spanish War, the United States defeated Spain and gained new territories such as Puerto Rico and Guam. The victory showed that the US had gained power and showed the world it was a strong nation.

After remaining neutral in WW1, the sink of the Lusitania and the Zimmerman telegram forced the US to enter WW1. After the War, the US lived a period of prosperity called "the roaring 1920s." In 1929 was the Great Depression that ended in 1939, just before WWII. After the war, many nations were in debt with the United States because of the loans they owned.

The other options of the question were a) the Balkan countries experienced a period of peace, B) the German economy was able to recover from its war debt, and c) Russia's government thrived under the czar's leadership.

The entry of the United States into World War I changed the course of the war, and the war, in turn, changed America. Yet World War I receives short shrift in the American consciousness.