By the First World War there was definitely propaganda contrasting American-Anglo-French "democracy" against German Kaiserism. I'm pretty sure there were similar ideological justifications for the Spanish American war too.

Going back into the 19th century the Democratic party emerged to elect Andrew Jackson on a platform that is by no means democratic by today's standards but was more amenable to the masses of poor white men than previous politicians or parties. The party was quickly taken over by slave owning aristocrats and actual democrats would next find their home in the Republican party some thirty or forty years later where they would briefly hold power before they were reeled in during Reconstruction. The next forty years after the civil war saw many democratic movements with varying degrees of popular support but none of them really wielded state power.