Before you go to war, you should be able to prove that the enemy did the attack. How do you prove this one? Circumstantial evidence of Russky subs nearby isn't really proof enough.
Now when our comsats get taken out, it'll be obvious who fired off the ASATs.
For starters, there are only a few navies that could pull off such an operation. Then reduce it down to friend or foe.
The Chi-coms are not there yet.
We know for sure the Russians have this capability.