Can Superman Stop a Comet From Falling To The Earth?

Yes..... that would be simple for Superman 

Although he's pretty strong, I wouldn't have thought he could do that!

In the Superman  video game,   that is precisely the first stage objective....

to save the city from a number of falling fiery meteorites . 

You have to race around and prevent any from hitting the city. 

I mean....no.  Not really.  But kind of yes also.

Look, Superman's power level fluctuates by era and writer.  He has, at times, been portrayed as bench pressing the weight of A PLANET for DAYS without rest in order to extract ONE DROP OF SWEAT from his brow.  

So clearly the weight of a comet, which is FAR smaller than a planet is no issue.  As long as he got out to it in time, he should be able to handle it.

But here's the rub, comets are moving very very fast, and they're not necessarily all that durable.  So if Superman went up to stop a comet that was already close to Earth, what he'd probably succeed in doing is breaking the comet into pieces that would fall to Earth independently, causing damage to be more widespread, though perhaps reducing the energy of any one of those strikes.  

One of the cheats of Superman...and really all superstrength characters. .. is the way writers have the power the exert not overwhelm the object they're manipulating.  A Superman who attempts to save a plane falling from the sky would just succeed in rending it's fragile aluminum skin.

At least one Superman writer attempted to explain this by saying Superman's strength isn't REALLY strength so much as a touch-range telekinesis wherein his strength is distributed safely over the whole object.  Which, y'know, A for effort, but I'm not buying.

No because he doesnt exist 

He doesn’t exist so no

Yes but only if it's falling on the USA.

We all know he can come on