Unless the response is ordered by a non-human entity (like a 'doomsday computer' ;>), there will always be a choice. But you're probably right, simply because the guy in the White House apparently wants to escalate things, to secure his reelection and place in history...
If Nato/EU gets hit by massive indirect nuclear fallout (drifting wind) because a Commie-Neocon warmonger in the Kremlin decided to escalate the war by launching tactical nuclear bombs on Ukraine... well, THAT is the escalation!