Watchmen Semiotics in Graphic Novel vs Film

Watchmen: Aliens vs. Doctor Manhattan as the "evildoer"

In the graphic novel, the story's main antagonist, Adrian, ends up saving the world from nuclear war by building fake alien-like creatures that teleport to some of Earth's major cities and explode, causing countless millions to die.  This is just before the United States and the Soviet Union (U.S.S.R.) are threatening to go launch nuclear war.  However, thanks to Adrian, the United States and the U.S.S.R. decide to put aside their differences in order to help each other and fight this new and unknown threat.

Meanwhile, in the film, Adrian actually ends up tricking Doctor Manhattan, the only superman-like superhero among the film's protagonists (who's powers are actually more nuclear-like in nature), to storehouse some of his power in generators; Adrian then precedes to transport and detonate these nuclear generators (which can be traced to Doctor Manhattan) in multiple cities across the world, thus pinning the blame on Doctor Manhattan instead.

Now, the question of how this changes anything may be raised.  After all, in the end, the film still ends the same way.  Both the U.S. and U.S.S.R team up to battle what they perceive to be a third-party threat, the members of the Watchmen still agree to remain silent (except for Rorschach, who is killed in both movie and graphic novel), and Doctor Manhattan still leaves earth by the end of the story to live in exile.  However, I feel as though the graphic novel leaves the world in a more chaotic state, as threat from a new-found (yet unknown) alien species makes it so both the U.S and the U.S.S.R. leaves them with a sense of ambiguity about who the real threat is.  At the same time, the ambiguous alien threat as depicted in the graphic novel could also represent how uncertain people were about being attacked during the end of the Cold War era and how everyone essentially felt unsafe and insecure.  Meanwhile, in the film, everyone knows who Doctor Manhattan is and pinning the blame on him gives the U.S. and the U.S.S.R. a common and known enemy that they can identify and makes the threat that they are facing seem a lot less ambiguous and a lot less dangerous.  As the Watchmen film was made in 2009, two years before Osama bin Laden was killed, this seems to make some sense.  Much like Doctor Manhattan, Osama bin Laden was a known threat the U.S. for many years following the 9/11 attacks.  Similarly, both Doctor Manhattan in Watchmen and Osama bin Laden in the real world were both identifiable and it is readily apparent to everyone that that they represented a threat to the world order (although Doctor Manhattan was framed, but I'll overlook that detail for arguments sake).