I would say the threshold is WWI, the blurring of the distinction rapidly picked up pace during and after WWII.
Well, I won’t quibble over exact time frame. The point I was making is the absolute sea change in definitions. Sound familiar?
Even the word itself “Democracy” is not mentioned, not even once, in the Declaration of Independence, the Constitution nor the Bill of Rights. There’s a reason for that, and it is because the government was setup the way it was precisely to try and prevent what is happening now.