I think the new ending works much better for the movie going audience that hasn't read the graphic novel then the original.
And besides, be it with a giant squid or tricking everyone into thinking Doctor Manhattan went crazy and killed a bunch of people, Veidt has accomplished his goal of getting the world to unite.
Because a cold war America's enemies wouldn't instead take that moment to gang up on the country but instead would unite with
I'm not even a fan and even I can see the new ending is lame.
According to the spoilers I've read Veidt has multiple Doctor Manhattan bombs which he detonates in cities around the world, so yes it would unite the world against Doctor Manhattan.