I mean widely spread. No doubt, individualistic ideologies could be found among intellectual elites. But most immigrants to this country were anything but intellectual elites. In all likelihood, they were European or Asian peasants or workers whose "native" cultures strongly emphasized social solidarity ties. They never heard of Emerson or the Whigs - let alone consciously following their counsel. So if that ideology becames widely spread - we need to look for the vectors of that dissemination. Immaculate intellectual conception does not sound very convincing.
wojtek