Well, that assumes they care about British expansion in Africa, which they really don't. Britain isn't really seen as a major enemy in this TL, at least not yet.
It may have been, by representatives of the new Liberty Party spoken of in Part Two. But they have so little influence in Congress that they have no chance of getting anything passed. In the ATL, a lot of the things that lead white people in the North to reconsider their views on the worthiness of blacks for citizenship, never happened.
The Emancipation Proclamation was never issued. Black men never served in the Union armies during the war, and they haven't been allowed to serve in the Indian Wars, the Franco-Prussian War, or the Spanish War.
Remember, in the years prior to the Civil War, the North was actually REGRESSING on that issue, with most states which had previously granted citizenship to free blacks revoking it during the 1830s, 1840s and 1850s, and many of them passing legislation banning any free blacks from even entering their States. There had to be some major contribution by blacks which was enough to convince the majority of white Northerners...who were at least as racist as white Southerners at that time...that free blacks were worthy of citizenship.
In OTL it was really the service of blacks in the Union armies during the Civil War that lead the majority of white Northerners to come to that conclusion. Since that never happened in the ATL, the path to black citizenship in the United States is going to be a difficult one indeed.
So I guess, to really get the ball moving on Citizenship for Blacks, we would need to see a particularly nasty atl Great War, in which free blacks or even slaves work side by side with the Union Officers? Also how about that list of States that have abolished slavery?