[Vicomte13]

"Given that the southern states that seceded from the Union were not considered a part of the United States for the purpose of the Emancipation Proclamation and the passage of several Constitutional Amendments after the war..."

I think we need to question some assumptions here.
The southern states were part of the United States for the purpose of ratifying the post-Civil War Amendments. Here is how Southern states voted to ratify, and when:

Tennessee, April 7, 1865; Arkansas, April 14, 1865; Connecticut, May 4, 1865; New Hampshire, July 1, 1865; South Carolina, November 13, 1865; Alabama, December 2, 1865; North Carolina, December 4, 1865; Georgia, December 6, 1865.

Ratification was completed on December 6, 1865.

The amendment was subsequently ratified by Florida, December 28, 1865 (Florida again ratified on June 9, 1868, upon its adoption of a new constitution); Texas, February 18, 1870.

The amendment was rejected (and not subsequently ratified) by Mississippi, December 4, 1865.

[Question_Assumptions]

As this page points out, there were certainly some "irregularities" in the involvement of the Southern States and their governments in their passage. For example, the 13th Amendment passed through 2/3rds of the Congress without representation from the Southern states.

Let me put it this way, why do web sites talk about Confederate states being "readmitted" to the Union if they never left?

[Question_Assumptions]

FYI, before you start arguing against a straw man, I'm a "yankee" who thinks that Lincoln ultimately did the right thing and not a pro-confederate revisionist.