Is there any action that could have been taken? Genuinely curious, I read about a test of some technology for deflecting asteroids a few weeks ago on HN, but I don't think we really have those capabilities yet?
There is likely a capability in the classified world to launch a vehicle to hit this object, but it won't be used because disclosing this ability would spark an arms race.
“Hit” and “do something useful” would seem to be distinctly different questions. A rock that you discover just before it hits us can’t be easily deflected, and even if you destroy it all of the mass is still headed our way.