May 14 1919, Paris–The Allies were well aware of the Armenian genocide, from reports of both survivors and neutral observers, and there was strong public support for the Armenian cause in the Allied countries. Although the Armenians had secured their independence the previous year at Sardarabad, they still faced threats from the Soviets to the north and the Turks still occupied large amounts of territory that had had considerable Armenian populations before the genocide. The Armenians recognized they needed outside protection, especially now that their usual patron, the Russians, could no longer be relied upon.
In late February, an Armenian delegation to Paris asked for recognition, large territorial concessions from Turkey, and protection under the United States. On May 14, Wilson agreed that the United States would take on Armenia as a mandate under the League of Nations. The proposed area was huge, stretching as far as the Mediterranean (and thus running into French claims in the area, though Clemenceau did not object). This was a promise that Wilson must have known he could not fulfill; he had even previously told the Supreme Council that “he could think of nothing the people of the United States would be less inclined to accept than military responsibility in Asia.” The Senate, under Republican control, would certainly not agree to an American mandate over territories of a power they had never been at war with.
Sources include: Margaret MacMillan, Paris 1919.