IMO, the South was improved by Northern conquest. The US has been in a constant struggle to improve itself... and has often failed, but has made progress at times... But back to the question I asked you; are you going to answer it?
IMO, The whole country was made far far worse by the overthrow of the original constitution, the removal of restraints on the power of the federal government and the conversion of the from a voluntary union based on consent to a centralized empire based on force, threats and violence.
back to your question, does consent of the governed include the slaves? Yes it did. It also included Indians and other ethnic minorities and women. None of them could vote either. None of them were asked what they thought either. Yet at the time, the 13 colonies that joined together to create the new Republic were easily the most free societies on earth. That they wouldn't meet current standards to be considered real democratic states now is irrelevant. Nobody else at that time would meet that standard either.