The pretended confederacy had no legal existance. Their money has no legal value. Debts to them need not be paid. It never had any title to the territory which it claimed.
It was a pretended government. Rather like Charles Stuart of England, aka the “young pretender” in his waning years he was an old man with a brilliant future behind him.
Most of those who fought for the south were conscripts, they were themselves slaves of the state.
Lincoln once said that anyone who supported slavery should find out more about the institution by becoming a slave themselves. Ironically, the southern soldiers were enslaved to fight for slavery, and many deserted, not caring for the institution or the cause.