Trade restrictions introduced by Britain to impede American trade with France, and both sides turned to the U.S. for economic help. The end was kind of a tie because nobody won. The United States fought powerful Great Britain, and, though there were no real gains from the fighting, the United States showed the rest of the world that it could fight Britain as an equal.
The treaty of Versailles blamed the Germans for causing the war, even though it was the Austrians who started the war. The answer is that the allied powers blamed The Empire of Germany.
