This means that either the US has CIA agents embedded in the Ukrainian high command, someone in the Ukrainian high command is dirty and is sending the US vital information Agent Werther style, or the US itself carried out or authorized the attack using Ukrainian assets.

On the other hand, if Ukraine is uninvolved, then the US has either propped up their own little terror group, or given some remnants of ISIS the resources to carry out this attack, and any communication as to how the US knew about the attack would blow their plausible deniability.

Exactly 0 of these possibilities are good, and the US has dug itself an enormous hole. This is going to absolutely blow up in the US' face.

I mean how would that even look?

"Oi, Russia, we're gonna hire some goons for a terrorist attack, watch out. - sincerely, CIA"