But the British deeds were done away with. They held no future sway. Compensation may have been paid, but that was after the fact. Efforts to pay compensation to the Union for Fort Sumter and other facilities were made, but these were deliberately rebuffed by Lincoln. He didn't want to settle the matter peacefully. His backers in New York stood to lose enormous amounts of money if the South was allowed to establish it's own trade with Europe.
The Union was perpetual and not dissolved by the choice of one or more states.
So was the United Kingdom, but we found this thing called "natural law", and it convinced our founders that no one had the right to hold people in allegiance against their will, and so they wrote the Declaration of Independence which says it is a right of nature and of nature's God for people to have independence if they so wish.
The constitution explicitly gives the fed gov the power to suppress Insurrection.
It isn't an "insurrection" or a "rebellion" when states vote to leave the Union. It was called an insurrection" to unleash those powers, but that was a lie.
Chief Justice Samuel P Chase said that "secession is not rebellion" and he also cautioned Federal prosecutors not to bring Jefferson Davis to trial, because if they did, they would lose in the court room everything they had gained on the battlefield.
The trial would have exposed the lie that was used to unleash all that power on the South. The Federal prosecutors wisely chose not to pursue this idea further in Court.
There were no effective financial institutions in the South capable of handling the finances required for the region to establish a direct relationship with foreign nations. Nor would any European power recognize the rebel as a legitimant government, not even Emperor Napoleon.
You obviously know nothing about Lincoln since he made repeated attempt to quell the rebellion. No president would consider surrendering federal property.
As to Lincoln’s “backers” International banking was much more important than that in NY, Boston or Philadelphia.
There was no authority for the South to rebel no matter how many “conventions” were called. There were several in the 1850s which only generated a lot of hot air. Every state that joined the Union agreed to creating a perpetual Union and some of the Southern states were even created by the Union.
Just as there is no illegal method from getting another union dissolved but through the courts, there is no reason to think such an act could be taken unilaterally. It would destroy the very meaning of “Union.”