When World War I began, many Americans were reluctant to join the war to avoid involvement in Europe's "petty squabbles" (as it saw them), and didn't feel that it was a threat to the US. They did send Britain essential war materials to help them during earlier parts of the war. The First World War saw a continuation of America's Isolationist policy, as the people of America didn't want to become involved in foreign affairs which didn't concern them. America did join the war, however, after Germany sank the Lusitania, killing 128 American citizens. They only entered the war for the last year though, and if they had come in sooner , the war might have ended much earlier.
