One interesting butterfly could be Reparations.
According to
this professor's course outline several bills to give land to freemen were passed by congress and then vetoed by Johnson (see III A). These are the source of the "40 acres and a Mule" myth.
They go in two directions: the "South" plan of subdividing plantations among the former slaves and the "West" plan of granting land out west, typically along the Union Pacific rail line (added benifit: protection of the RR).
Assuming Lincoln signs one of these bills (I have no idea if he would, but my gut says "yes"):
The Positive:
* This could mean that African Americans grow to be a class of petty yeomanry rather than suffer the quasi-serfdom of sharecropping.
* This might in turn butterfly the Black ghettos, though we probably still see a diaspora into the cities but this time by way of youth seeking adventure and advancement rather than desperate penniless refugees escaping sharecropping.
* Could an self-supporting "model minority" black population possibly avoid some of the racism that accompanied OTL's "poor ignorant" black steryotypes?
The Negative:
* Possibly lead to even greater clashes with southern whites over this "handout". This is particularly exacerbated in the South plan. Poor whites, now the principle sharecroppers ATL, might be even more bitter towards blacks.
* Increased clashes between blacks and indians in the West option. This could lead to movements among the blacks feeling they were "sent out to die" fighting indians.