The US is not a democracy; at least aspirationally, we're a liberal federal republic with a "mixt constitution".
The "mixed" part includes a large dollar of monarchy with a president who's chief of state and head of government (or head of state and chief of government, and screw it, I'm not going to look *that* up again). The Senate was initially designed to represent the States and to be the aristocratic element, and for good and for ill it's kept a lot of the aristocratic bits.
And we common ruck got the House of Representatives and elections.
From the Bill of Rights on, we've had the liberalism of limited government with a People with "unalienable" rights, and eventually and most of the time a judiciary that aren't "lions under the throne" working for the king, but an independent branch of government having final say — in theory — on the meaning of the Constitution and laws. (Check out Andy Jackson and the Indians on the "in theory" part.)
This is all important, because "democracy" has some literal meanings and history as well as the warm-and-fuzzies of a complimentary term. It's a bit part, but the nominal hero of Aristophanes's THE CONGRESSWOMEN gets to summarize a whole lot about Athenian democracy when he identifies himself as "I'm Athenian, male, of age, and free." I.e., he's a native and not a resident alien, a girl or woman, a boy, or a slave. He's part of the _demos_ which was only a relatively small part of the population of democratic Athens.
A lot of the history of the "liberal" part of "liberal (republican) democracy" is expanding that "demos" in "democracy."
The US formula for a long time was "free, White, and 21," with "male" and often "Christian" going unstated: that was the effective demos. We may be heading back to that idea, which will not be good for republican institutions and liberal protection of people who's ancestors weren't free in the USA, are not White — and who's White and who's not has been complex historically — and maybe young and on their way to inheriting messes their elders created ("Posterity don't vote").
And "male" can also get complicated: "Real men" and all that.
I'm a member of the Democratic Party and fond of democracy, but I swore allegiance to the Constitution and a Republic in which institutions and norms are supposed to keep any part of government from growing tyrannical, including a self-defined Demos that comes to see itself as a Nation and "The People" (who count) and an arrogant, exceptional, downright Chosen People at that.