For reference, in case anyone wants to see what we're talking about more directly:

https://cascadiabioregion.org/nine-regions-of-cascadia

(I picked this one because I am a blatant Seattle Supremacist /s)

So yeah, you'd have to overlay this kind of a map with say, county level political maps for the US, apologies to Canadians, I do not know what the Canadian approximate equivalent of a county is.

But yeah, then look at rivers, origin points, watersheds, dams, other critical infrastructure, etc, to see how this could possibly shake out.

The Greater Idaho idea was originally to essentially carve off as many counties in eastern WA and OR, basically east of the Cascades, and... move them into Idaho:

https://moveoregonsborder.org/the-maps/

I ... guess they gave up on trying to take Spokane.

But uh yeah so basically everywhere between the Cascades, down to Medford, down further to Redding... would potentially be a war zone.

Like, I5 south of Portland would be a critical artery and thus a warzone, probably same with I90.

Personally, if this happens, I'm counting it as yet another thing Deus Ex ended up predicting.

There's a conversation you can have with an ex NSF soldier, who tells you about how his squad got wiped out at 'Squalnomie', by other troops with thermoptic camo.

Squalnomie -> Snoqualmie, as in Snoqualmie Pass, I would assume.