I’m beginning to believe you are a troll - I mean what the hell could NASA do about it if one was heading straight at us? Answer? Fuck all!
And there you have it in a nutshell. I often post tongue-in-cheek ‘How do you get rich beyond your wildest dreams?’ Answer - get yourself a government contract; they’ll keep chucking so much money at you’ll be sick of the sight of it! 
No but you are certainly becoming one.
NASA could give us as much warning as possible, give us the size, speed, target area, and potential damage allowing us to have at least some warning and a chance to prepare.
If they can detect one far enough out that is going to hit us they can provide us options for trying to break it up or change it’s orbit enough to cause it to miss.
If there was nothing NASA could do about it except warn us, then personally I’d rather not know it size, speed, or target, thank you very much! Especially if the ‘space rock’ was as big as the one that ‘wiped out the dinosaurs’ (so they say, and if anyone believes that they’ll believe anything!); I mean to ‘wipe out’ the dinosaur populations of every country on the planet, that must have been one hell of a big space rock? As to diverting an incoming asteroid, or ‘breaking it up’, I suspect you’ve been watching too many space disaster movies?
Fortunately you don’t get to make those decisions for the world. Hide in your basement and cut yourself off from all media if it bothers you that bad.
If we get enough warning diverting them would be relatively easy, we’ve already proven our capability of landing a probe on one.
Even a .0001 degree deviation millions of miles out would push an asteroid or comet far out of our orbit. Speeding it up or slowing it down even slightly takes it out of our oribit. Lots of ways to accomplish that.
Destroying a meteor would be much more difficult, comets, not so much since they are just ice.
And if you really believe that . . . seriously believe it . . . then there’s no hope for you.
I have no problem accepting what is proven through science.
Hell fifty years ago we were able to build rockets powerful enough to get us to the moon with slide rules and pencils and most of the calculations to get us there were done by hand as well.
NASA needs all kinds of money to finance the “Space Corps” that already exists. Humans have been to all corners of the Solar System and beyond. Only sleepers think Earth is flat or we’ve never been to anywhere
Nor do I - in fact I often ask ‘Where would we be without it?’, but fake science is another thing altogether. The moon is on our doorstep (and you won’t be surprised to know that I have my doubts that we went there too. lol). So that’s a bit different to reaching planets 60 million, million million miles away from Earth. doncha agree? I can’t believe I’m having this conversation!
Of course it’s different but we’ve had the basic tech necessary to get us to Mars for decades and it has continually improved.
What challenge is it you think has not already been addressed required to get us there?
That is so nonsensical that I’m almost affronted by it.
So you have no answer as expected.
The question was so oblique that I didn’t have the faintest idea what you were asking. Try putting it in a more coherent fashion and I’ll answer it.
It’s completely coherent. What technological gaps still exist in your mind preventing us from being able to get to Mars?