U.S. planned "rigorously" for Russia using nukes on battlefield in Ukraine

When you say ‘every conceivable scenario’ and that they do do ‘especially silly’ ones; does that just include exceptionally unlikely but architecturally plausible(urgent need to annex Canada, say, seems most unlikely to arise; but would be nontrivial if it needed to be done); or does it genuinely include ‘especially silly’ ones on the scale of “Antigua becomes hyper-militarist bellicose nuclear power”; rather than just “Antigua: what’s the best regime change you could deliver?”

My layman’s assumption would be that some things are just too contrafactual to be educational(unless they are being used strictly as a name change/palette swap, the way some video games use “North Korea” as an opposing force when they really mean “China”; but don’t want the hassle of upsetting someone commercially relevant and prickly about their image); but I’m curious because me spitballing is of obviously lower relevance than someone who is actually familiar with the matter.