Explain three important changes that occurred in the United States during World War 1.

Woodrow Wilson was President of the United States at the time, and initially tried to keep the US out of the war. While Europe had been fighting since 1914, the US didn't start sending troops until 1917.

One of the biggest changes in American society during WW1 was the role of women. Most of the able-bodied men were drafted as soldiers, but the war required an unprecedented level of materiel that had to be made in factories, so there was a shortage of factory workers. Factories began to employ women---over 3 million by the end of the war---and as a result, formal employment for women became much more common and much more expected. This sowed the seed of changes in the role of women in society in general, and likely contributed to the success of the Women's Suffrage movement that gave women the right to vote in 1920.

The tax system also changed dramatically in WW1; the income tax had only just began in 1913, and at the time it was very small. But during the war, the need for huge amounts of government (specifically, military) spending led to a surge in tax rates, which raised the top income tax rate from just 15% all the way up to 77%. This made taxes in the US not only much higher, but also much more progressive---and laid the foundation for the current tax system which is now heavily based on progressive income taxes (albeit not quite as progressive anymore).

Finally, civil liberties in the US were curbed during the war, not unlike the erosion of civil liberties that happened in the aftermath of 9/11/2001---but if anything even more severe. The Espionage and Sedition Acts didn't just affect actual espionage and sedition, but essentially criminalized protesting the government. This was argued to be necessary to maintain order and win the war, but it deeply undermined free speech and freedom of association. The US Postmaster General was given the authority to ban anything sent through the mail that even criticized the war effort. The Sedition Act was repealed in 1921, but the Espionage Act was only slightly weakened, and the precedent was set for eroding civil liberties during wartime.