The U.S. started a direct war (in all but name) with Russia.  If Russia doesn't respond to that, it sends a signal back to the US that they can escalate it further.  Those escalations will not stop until the American people push back.  The question is whether they would push for descalation or they would push for revenge.  History shows us that most people push for revenge... and so yes it would probably just escalate further.

But how then does Russia defend itself?  Must it lay down in defeat and let Anthony Blinken fly in and take over the Kremlin?

My thinking here isn't advice to Russia. I'm trying to suss out what they might do by putting myself in their shoes.  And I don't have a good prediction at this point, but this discussion does help.