What's the significance of 9/11 for American democracy?
The way I see it 9/11 allowed people who were always against freedom to openly speak up about it. You see, before 9/11 we had this thing called respecting the American revolutionary tradition, which involved saying that you were for freedom of speech, freedom of assembly, etc..even if you really hated 99.9 percent of what people actually said or what they assembled for.
9/11 freed those people of having to even give lip service to ideas they truly didn't believe in.
It also, conversely, makes people who speak for freedom more authentic these days, since it isn't like everyone is using the word freedom anymore. At least not in ways which are openly lies; these days you can tell who really means freedom and who just uses it as a propaganda device, way back when it wasn't quite that clear.
So, in other words, people have the freedom to declare that there's too much freedom in America now, and people also have the freedom to say that there's too much authority in America right now.
I personally don't think we'll ever get back to some pre-original sin days where people who hate freedom say they love it, no, I think that the political realignment which is happening, where a far right which is anti-freedom is forming, and a far left which is radically pro-freedom is coming into existence, is here to stay.