Having nuclear missiles ready at all times, all over the world (near populated areas) is a risk on its own... In a politically stable world without conflicts, sure, but we haven't had that kind of world for centuries...
Even if you were gonna hit the meteor during significant downward trajectory (which seems unlikely), that would still have to be done at quite a distance from the impact location.
Also wondering when there was ever a "politically stable world without conflicts"
In 9 out of 195 countries.