Point of Divergence
On April 14, 1865, Abraham Lincoln is assassinated by John Wilkes Booth. Less well known was the assassination of Secretary of State William H. Seward by Lewis Powell. In OTL, Seward survived the attempt, and went on to negotiate the purchase of Alaska from Russia. In this ATL, therefore, there is no one to convince Congress to purchase the seemingly-worthless territory, and it is eventually purchased by Japan.