In the context of feudalism, monarchy and the late "Middle Ages" in Europe, liberal democracy is one of the most revolutionary things ever to happen to Humans, and the US led the way in reducing that ideology to practice.

From there, the admirable stuff is largely the framework for self reflection the system creates, though the US has not always led the way in that sense compared to its peers. No society is perfect, and a major differentiator between empires is how the people handle reflection of past sins. This is why being a progressive in the US is so fucking tedious - because the legacy and the procedures for doing better are there. They are well known and they aren't that complicated. But then there's this whole contingent of reactionary assholes who are neither students of history or philosophy, resting on imagined laurels to constantly oppose and then undo what progress we are able to make.