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. 

 They started a proxy war the minute they started flying refueling loops. This is a progression, sure, but it doesn’t really mean anything. I could see Russia pulling an Iran, maybe, as a response: flinging some missiles in the general direction of an American installation and then saying, “This matter is concluded.” But that’s about it. 

I’ve been of the personal opinion that the US’s plan is just to continue to keep this going for as long as possible, with Uncle Sam providing the goodies. I don’t think there’s a Russian regime change on the horizon, either. Nobody really wants peace, and Russian ineptitude guarantees there will be no real victory. And I think the powers that be are fine with that. 

 I think that "US interests" want to spend all the allocated money while they can, because they clip that ticket and want to be paid as much as they can be paid.  But there are other ways to embezzle and cheat the American taxpayer without also escalating a conflict against a nuclear power.

I don't think a Russian regime change makes any sense at all for the West.  Putin is one of the doves.  A regime change would escalate the war significantly.    Okay, now that I typed that out, now I understand why they want a regime change.  They want a bigger war.