The Civil War had a greater impact on American society in the polity than any other event in the country’s history.
Churchill was asking the United States to help fight along British's forces in Europe.
Answer: Following the assassination of Franz Ferdinand, Austria Hungary was hella mad about it, so they went to Germany, and was like hey, help us get revenge on Serbia. So the two of them teamed up and declared war on Serbia on July 28th. Shortly after (a couple of days) Germany declares war on Russia, and then after Serbia's ally invaded France, that pushed Great Britain to declare war on Germany.
(hope this helps)
