[T]he way I see it, even to early Americans, who saw the black men in their midst as property, American identity was not centered on whiteness; just because blacks were seen as different doesn’t necessarily mean whiteness per say had any great role in white Americans’ notional conception of themselves. In the whole of their daily lives, other than in their dealings with what at that time was seen as a specie of property, whiteness played no role whatever. Why, after all, would your identity center upon that which distinguishes you from a specie of property.By no means all Americans back then regarded black people as property. The northern states abandoned slavery long before the Confederacy was required by force to do so.
I don't know if my great-grandfather Jacob counts as an "early American" in the grand scheme of things: the news of Lincoln's Gettysburg address reached him in Lyons, New York at the same time as word that his brother had been wounded in that battle. He immediately enlisted in the New York artillery and went on to serve under Sheridan in the Shenandoah Valley campaign.
I can't be sure, of course, but I should think Jacob joined the Union Army for a variety of reasons, both personal and political. These were times when many men examined their conscience and found it led them to enlist.
I don't imagine Jacob joined up to fight for "a more perfect union", nor do I suppose he was fired with Abolitionist zeal (few of his fellows were so inspired). But whatever his reasons, and those of hundreds of thousands like him, in so far as such men thought about black people at all, they mostly thought of them not as "a specie of property" but as comprising (through the instrument of slavery) a form of unfair competition that was likely to undermine the wages and conditions of free labor everywhere.