Not the OP, but the best way to contrast liberalism is from the perspective of Puritanism. Puritans were certainly not liberal socially, but they were also not

Not the OP, but the best way to contrast liberalism is from the perspective of Puritanism. Puritans were certainly not liberal socially, but they were also not liberal governmentally - many of the laws in Puritanical societies were highly restrictive, and pre-modern liberalism had its roots in creating a more free society - Puritanism is a non-negligible part of American history. Modern leftism tends to be more authoritarian - it encourages restrictive legislation as a mechanism for progress. This is the dystopian future alluded to in a lot of e.g. Heinlein's work - things like forced sexual liberalism, erosion of parental rights or even parentage itself, elimination of the individual for the cause, and discrimination against the individual based on factors outside of their control. Americans tend to view political affiliation as a binary - left or right, progressive or conservative, liberal or authoritarian. That's because, due to our history, we have always tended to have a leftist, progressive, liberal party contrasted with a right-leaning, conservative, authoritarian party. That language is in and of itself somewhat complex - prohibitionists were considered progressives in their time, though today we would view them as otherwise.