All the advantages you're talking about are very temporary. The blue states have production, manpower, and allies. Enlisted military people skew right and independent, but enlisteds don't control the military. The right may want to "expanbd" and they may even try to but blue states would both have nuclear deterrents and all the advantages of long-term-warfare on their side.

You are right that the blue states may just refuse to secede, but if they do, the right won't be able to stop them. Saying it could is just fundamentally not a materialist analysis.