Actually, we might well be able to do something. For one thing we could likely have decades of warning. (The searchers are not authorized to project orbits further into the future than 100 years.) With that kind of warning it is likely that very cost effective solutions could be devised. The object that caused the Barringer Crater in Arizona about 50,000 years ago (a eyeblink in cosmic time) was only a few meters across. The meteor that released about 200 times more energy than a hydrogen bomb over Tunguska, Siberia in 1908 probably never even impacted the earth, merely glancing off the atmosphere.
If we could change the velocity of an asteroid by one inch per second ten years in advance, we could change its trajectory by more than the radius of the earth ten years in the future.
Really?
I'd guess that the orbits can't be calculated that far into the future for such small objects due to gravitational influences of large (planetary) masses.
Look, we know the threat exists. It would be better to develop a defensive method first or in conjunction with the search.
Knowing without the ability to change it will just cause frustration and panic.