Well, for starters (and ignoring all other implications) you'd have lost a minimum of 3.4 million people, so basically over a million and a half working adults, and of course all their descendants. That's not insignificant and they'd have to be replaced by somebody.
Convention on the Prevention and Punishment of Genocide
[...]
Article II: In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
(a) Killing members of the group;
(b) Causing serious bodily or mental harm to members of the group;
(c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
(d) Imposing measures intended to prevent births within the group;
(e) Forcibly transferring children of the group to another group.
At the start of the civil war there were 4.4m blacks in the U.S. Your challenge is to reduce this number to less than 1m by the year 1900 without mass genocide. And if the back population were reduced how would that effect the U.S.
This isn't ASB. This is the back to Africa movement.
https://en.m.wikipedia.org/wiki/Back-to-Africa_movement
If we want to get this done before 1900, we need to avoid both reconstruction and Jim Crow. Have Lincoln survive and (by embracing his innate racism) attempt to reconcile with the South. An easy way to do that would be to ship out freed former slaves.
The blacks are moved to the Oklahoma territories,.
This isn't ASB. This is the back to Africa movement.
https://en.m.wikipedia.org/wiki/Back-to-Africa_movement
If we want to get this done before 1900, we need to avoid both reconstruction and Jim Crow. Have Lincoln survive and (by embracing his innate racism) attempt to reconcile with the South. An easy way to do that would be to ship out freed former slaves.
Building the Panama Canal starts earlier (before 1870) newly free slaves are offered land and money to move there to Panama to build it.
Forced migration IS genocide.
At the start of the civil war there were 4.4m blacks in the U.S. Your challenge is to reduce this number to less than 1m by the year 1900 without mass genocide. And if the back population were reduced how would that effect the U.S.
Have Southern state governments get behind sending blacks to Haiti, other parts of the Caribbean, and Africa (Liberia, of course, but possibly other parts of Africa). Have the US government in general emphasise this and maybe even give incentives for this migration. The South can replace the lost labour with European immigrants, and possibly Chinese immigrants as well.
The problem is that the southern governments didn't particularly want this, they had a nice arrangement where blacks were serfs and can be easily kept under control with passbooks and jim crow laws. They basically fought a series of race wars against freed African slaves during the reconstruction and won. In this sense, having blacks was actually a necessity to preserving something like the antebellum south in the late 19th-early 20th century.
Importing white European labor or even Chinese immigrants to replace them means you've effectively overturned the entire southern social order: which is the very thing the southern elite wanted to avoid the most.
Forced migration IS genocide.
I don't think that you people are aware of the magnitude of the numbers: 3.4 million people is about 80% of 2015 population of Panama or Liberia.