How did US involvement in World War 1 directly affect the course and outcome of World War 1?

On April 6, 1917, two days after the U.S. Senate votes 82 to 6 to declare war against Germany, the U.S. House of Representatives endorses the decision by a vote of 373 to 50, and the United States formally enters the First World War. President Woodrow Wilson pledged neutrality for the United States, a position favored by the vast majority of Americans. Britain, however, was one of America's closest trading partners, and tension soon arose between the United States and Germany over the latter's attempted quarantine of the British Isles.
Fundamentally, as the massive Russian army left and the massive American army came in, there was not much difference or consequence, as America did not join the League of Nations,or make many post-war decisions for Europe besides Versailles