In terms of ethnic diversity, there was a sizable segment of US population that was of German and Austrian origin and was reluctant to see the US attack the country of their ancestors; especially considering that the war remained morally ambiguous.
In terms of socioeconomic diversity, most left-wingers and pacifists considered that it was an imperialistic war in which competing empires were sacrificing millions of young men for the sale of imperialism and ultra-capitalist profit (arms sales).
In terms of political diversity, most Americans remained isolationist, including the president Woodrow Wilson and they did not want to be involved in a war between foreign nations in faraway lands.