There is nothing in the rules stopping RM attacking New York/California/Colorado/whatever, or LN attacking New Berlin/Stuttgart/Frankfurt/whatever.
However in the interests of sanity and keeping a logical nature to the war, I'd ask that conflict is generally speaking kept to the systems in which it's supposed to be happening. Those being Texas, Hamburg, Bering, Hudson, New Hampshire and Bremen.
I'll repeat, it is not against the rules to go elsewhere, it's just not great in roleplay terms.
![[Image: DramaticExit.gif]](https://sig.grumpybumpers.com/host/DramaticExit.gif)