Early American entry overwhelms Germany sooner

What changes if the United States enters World War I from the beginning?

American forces begin building up on the Western Front much earlier, confronting Germany with overwhelming Allied manpower in 1915 and 1916.

The United States would have to mobilise and deploy an army much earlier than it did historically. American forces could reach the Western Front quickly enough for the build-up to matter in 1915. The large troop surge that arrived later in the real war would therefore be brought forward. Germany would face overwhelming numbers during 1915 and 1916 instead of waiting until the final phase of the conflict. The counterfactual turns on manpower and mobilisation time rather than a single battlefield intervention.