A very significant point, not often discussed directly, was the seeming lack of unanimity among Americans of all political stripe, even at the very beginnings of the Union.
Unlike the New Englanders of an earlier time(War of 1812) the southern secessionists did not view the lack of a clear consensus, in or out of gov't, as a warning sign to go slow on its implementation.
Ironically, their(secessionists) act of trying to impose their interpretation on the United States, allowed Lincoln to impose his own.
P.S. when I mention Lincoln I do not mean to infer that it was his interpretation alone, merely that a consensus(from various interpretations of that time, including Lincoln) resulted from the winning of the CW by the Union.