Answer:
The United States entered World War I in 1917 as a result of a series of events that began with the assassination of Archduke Franz Ferdinand of Austria in June 1914. This event triggered a chain of events that led to the outbreak of war between the major powers of Europe.
The main cause of the war was the rivalry between Austria-Hungary and Serbia. After the assassination of Archduke Ferdinand, Austria-Hungary declared war on Serbia, which then triggered a series of alliances and declarations of war between the different nations.
In particular, Germany declared war on Russia and France, which then resulted in Britain joining the conflict. This was a result of Britain’s commitment to defend France and its colonies, as well as its commitments to defend Belgium, a nation that was invaded by Germany.
In the United States, the public was generally not in favor of entering the war. However, a series of events changed public opinion and eventually led to the entry of the United States into the war. These events included the sinking of the Lusitania in 1915, the Zimmerman Telegram in 1917, and the unrestricted submarine warfare by Germany.
The United States declared war on Germany in April 1917. This was followed by the entry of the United States into the war in May and June of that year. The United States played an important role in the war, providing economic and military aid to the Allied forces. This ultimately led to the victory of the Allied forces in November 1918.