I have two issues here: did it become a democracy before or after the Articles of Confederation? Some say that democracy was born when the America seceded from the British. Others say that not until the constitution. Some say that it wasn't until african americans and women could vote.
Secondly, this question is often deflected with 'America is not a democracy, it's a republic'. Regardless, for the purposes of this question, I'm assuming America's a liberal democracy.
I have the same problem as /u/blackbird17k. I don't understand your terms. The US is a federal republic. Each of the states has democratically elected officials and members of Congress.
The real question here is "what is a democracy"?
I don't understand your terms, and yes I'm going to say "America is not a democracy; it is a republic."
What do you think "democracy" is? What is a "liberal democracy?"
"Democracy" is often defined as a system of governance in which all people vote on laws. Athens is the quintessential example, and the one to which the Founders looked at (see like, all the Federalist Papers).
So since the U.S. is obviously not that notion of democracy, what do you think "democracy" is?