The TL works up until the alternative Franco-Prussian war expy, the Second Mexican-American War. Why would Britain and France still back the C. S. A. , when by 1881, the U. S. A. was nearly a match, industrially to Great Britain. I can't see a United States that was humiliated by the C. S. A. letting their Army and Navy decay. With a hostile neighbor on the U. S. A.'s southern and western border, the U. S. Army would be far larger, and the Navy would be kept up well. I am not sure James Blaine would be president, either.