Why did the Confederates states have to be re-admited to the "union" then? What about Virginia, New York, North Carolina, and Rhode Island & Providence Plantatations after the Constitution was ratified by the 9th state? What about Vermont, that was an independent state since 1777? What about Georgia, that was not a member of the Articles of Association, despite being in existance for decades prior?
It's been said many times in these threads that this is -not- what happened. The core Republican Party stance throughput the whole war was that the Union was indissoluable. That is why the great mass of loyal volunteers came forward -- to fight for an indissoluable Union.
What was at issue post-war was the seating of congressmen and senators. It was their "readmitance", not the states, that was at issue.
Walt