Watchmen movie ending, I'm so confused

Any brilliant minds here can shed a light on my very confused brain? I've just re-watched the movie again and I don't know why I didn't thought of more of the ending until just now.

So Ozy painted Dr Manhattan as the common threat against humanity. But then he decided to "move" somewhere else at the end of it. So— what's the "common threat" when he just leaves Earth? Wouldn't humanity give up chasing the impossible and start fighting amongst each other again? Shouldn't a "common threat" be present somewhere humans can fight?

Eg, Covid erupted and humanity stopped fighting each other and focused on the cure. Covid is still present now but that is no longer the focus any longer. Even a very present threat, humanity still hates each other. Am I thinking too far? Lol

Edit: Thank you so much for all your insights. I did read about the comics having a more present threat of some squid monster which makes a little more sense than VS a God. I just felt that Ozy doesn't realise (despite being the smartest man in the Watchmen world) is that humanity will always find a way to fight with each other.

Here's a more stupid idea: How about Ozy asking Dr Manhattan to transport those millions of people that he sacrificed to some other inhabitable planet for a month then only sending them back. This gives a warning to all humanity that Dr Manhattan "could" actually take all those lives but decided not to, giving humanity one last chance to consider war. It still paints him as a ever present threat, isn't it?