You are coming from a view that the resolution is there to be either affirmed or denied. (I believe the term is rezcentrist, but I might be wrong.) I would argue against this using parametrics.
You're right about my rezcentrism.
But that's a debate for another thread.
The negative team is negating the resolution because once the Aff team limits the resolution, everything outside of it is outside the resolution, and is now ground for the neg to CP with. So basically neg is not affirming the resolution, and is not extra topical, and as such your impacts don't matter.
That's my point - the negative shouldn't have claim to CP anything and everything outside of the resolution. That's inconsistent and unfair.
My argument fits in a parametrics framework too, though:
The affirmative's job is to affirm "[insert case]" and NOTHING BUT "[insert case]" (without going outside the resolutional boundaries)
Thus, the negative's job is to negate "'[insert case]". To make a comparison, we say that negating the resolution is equivalent to affirming the negative of the resolution, and thus the negative should affirm "we should not do the affirmative's case" and NOTHING BUT "we should not do the affirmative's case."
By affirming "we should not do the affirmative's case" AND "[insert CP]," the CP is extra-topical, and thus inconsistent and unfair.
So, no matter which framework you look at, the negative shouldn't do MORE than affirm the negative of the resolution, thus ruling out extra-topical (including states) CPs.
As a sidenote: Has anybody actually ran a states CP, or had a states CP run against them? At the beginning of the year, I thought they'd be very common, but I haven't really heard of any. Maybe a regional difference?