This timeline centers around three PODs: Samuel C. Pomeroy (a Radical Republican) becomes President Pro Tempore instead of Lafayette S. Foster. The Second one is that Atzerodt and Powell manage to kill Johnson and Seward, which causes Pomeroy to become president.
Later on, the economy was starting to tank. Pomeroy, while trying to be re-elected in 1868, is shot by a Southerner. This causes pure anarchy as new President Wade can't cool down tensions. The Senate finds a replacement for Wade, in the meantime.
The South, being the most hurt due to harsh reconstruction measures, secedes once more (Texas secedes as a separate country, and they take all of the former land in the west that the CSA claimed) (But, the CSA does have W. Virginia, Kentucky and Missouri). The Army can not control the situation anymore. It goes so bad that the election is postponed.
In 1869, Utah Territory's government is overthrown and is replaced by a Mormon Theodemocracy, led by LDS president Brigham Young. The new country is called Deseret. Wade tries to force Deseret into the union. Later on, the economy goes into full depression. Wade is later killed by an unemployed man on May 31st, 1869. The new president, Henry B. Anthony, decides that he is not ready for this job considering the current situations, resigns after only a week into office.
The Senate has not found a replacement for Anthony, so House Speaker Colfax becomes President. Colfax soon realizes that the only way that the United States can survive is that they accept secession, and decides to offer a peace deal to the CSA, Deseret and Texas. It is soon achieved.
The West coast, along with the Mountain states, soon secedes as well as famine is rampant due to a low economy and supplies taking a long time, they decide that they can better handle it on their own and try to become major trading partners. The Plains states, with their main export being crops, has suffered because of the economy, and secedes to form the Plains Republic. New England, taking some advice from the West Coast and the Mountain states also secedes. Colfax holds on to whatever the US has left. While the United States still exists, it does not control as much land as it did before. How will the world progress without a United USA?