Your challenge, should you choose to accept it, is to take any post-1776 POD and create a scenario where the ACW is not between North and South, but East and West.
What issues could trigger secessionist fervor in the western states (I'm thinking anything west of the original states + Florida)? How would the war itself go? Would the West have a better chance (my rough guess is yes, although I don't know how much of OTL's "Northern" industry was in the Great Lakes)? What do you, the readers at home, think?