Since this country does not now practise Slavery does that mean it is impossible for us to engage in another Civil War?

I am not taking about States against States Civil War as the last one. But I can see a Northern Ireland type of Civil War. A true rebellion. But what would be the reason for such a war if we do not have slavery to blame it on, since it seems that that is the only reason we find sufficent enough to go to war within this country accourding to these types of "Historian"?