"When Southerners were mass migrating to Northern cities, did people lament the loss of northernness?"
No, they were thankful.
In all seriousness, I don't think so, or at least it wasn't thought of that way. It was thought of as change, and as such, wasn't particularly welcomed.
I've lived all over the country, and the South is probably the area of the nation that still has the strongest regional identity, a distinct regionalism and is extremely proud of it. Don't misunderstand me, I'm not saying that other areas of the nation aren't proud of their area, but the South reeeeaaallly takes it to heart.