I conceed that there's no one here who can (or should try to) change your opinion. That's just not gonna happen. However, if I may address some of your problems with the film, you might understand where the filmmakers were coming from on certain issues/scenes.
I agree wholeheartedly that the Comedian was an unlikeable bastard. Won't bother disputing that comment one bit. The reason he cries about Adrian's plan is that, as bad a man as he knew himself to be, even he did not think himself capable of what Adrian was about to do. Adrian killed him because he couldn't afford anyone knowing his plan and therefore wielding the power to affect its outcome. It's explained a bit better in the graphic novel, and may yet be better explained by the Director's Cut/Ultimate Edition.
The world is in fact worse off because the US won the Vietnam War. Tensions with the Soviet Union are much higher than they ended up being in real life. The US government is essentially under a dictatorship, with Richard Nixon being President for Life, so that also has people a bit uneasy. Ultimately, superheroes are outlawed because, well, they're vigilantes.... and you can't very well run a "dictatorship" when your handpicked police and military aren't the ones rounding up the lowlifes. That's why The Comedian and Dr. Manhattan were allowed to continue, because they agreed to work for the government.
Finally, the issue of whether or not nuclear war unites the world. 9/11 didn't involve nuclear war, although I presume you just meant the "outside threat" part. It certainly proved that an attack on the city of New York (which is the ONLY part of the world that gets "attacked" in the GN) isn't gonna unite us, except maybe for 24 hours. A global attack.... which I hope and pray we NEVER have to deal with.... might stand a better chance of accomplishing this. But it's rather ambiguous. Indeed Laurie tells Dan that Jon would say, "Nothing ever ends." And at the New Frontiersman newspaper office, Rorschach's journal is seen amongst the "crank file," which indicates that there's a chance that Adrian's plan may yet still be exposed.
Again, I know I'm not changing anyone's opinions, but I hope that clears up a couple of the problems you had with the movie.