Final answer:
During World War I, the primary role of U.S. women in Europe was to provide medical care to injured soldiers, often as nurses or medics. They also contributed by working in roles that were traditionally held by men, such as in munitions factories and civil services.
Step-by-step explanation:
The main role of U.S. women who served in Europe during World War I was providing medical care to wounded soldiers. Women served as nurses and medics, and a significant number joined the Red Cross to offer emergency medical services, often near or at the battlefront. Additional roles of women during this era included working in munitions factories, civil service, and other traditionally male-oriented jobs, contributing significantly to the war effort and leading to social changes such as women's suffrage post-war.