The Formation of the United States in the 20th Century

Either the 13 Colonies never unified as one, or the American Revolution failed disastrously, was there ever a chance that the States could have united much later than in our timeline, on the largest geographical size possible?
(I don't know if I can actually place this in the "before 20th century'' section, since I'm fine with more than one answer)
 
Perhaps in one of those "no Constitution" timelines, the AoC putter along for a while, with sectionalism or slavery making some states leave.

You have some regional groups, and the Confederation as something like the Zollverain, but nothing like the USA. American filibusters still seize California and Texas, but the *USA they join is more like the German Confederation.

Then in the 1860s, Abraham Lincoln unifies the American Republic with Blood and Iron?
 
Top