Since it's been confirmed that C.C.'s been everywhere including America, won't it be better to make this a fic with historical characters, but based on the Code Geass world, if what you want is play with the Civil War themes? Your idea is sound, though, and I like the whole centralized and decentralized government thing....but :
There's also the problem silentorphan stated above. I myself have several thematic AUs floating around in my head, but whether they're simply re-creating the Code Geass situation in another continuity or integrating meaningful themes is another matter. Your Lulu would also need a vastly different Background Angst, if he's focused enough on revenge to fight for the Side That Has Slavery, state rights or no. Lelouch hates violation of human rights Except When Necessary (he thinks), but he doesn't seem to care that much for political ideals in actuality.
*puts on concrit hat*
There's also the problem silentorphan stated above. I myself have several thematic AUs floating around in my head, but whether they're simply re-creating the Code Geass situation in another continuity or integrating meaningful themes is another matter. Your Lulu would also need a vastly different Background Angst, if he's focused enough on revenge to fight for the Side That Has Slavery, state rights or no. Lelouch hates violation of human rights Except When Necessary (he thinks), but he doesn't seem to care that much for political ideals in actuality.