> To be able to enter into new long term agreements, we must respect existing agreements.
That is a matter of trust, it's not an obligation for the state. We are a society of people, and for us to perpetuate civil society, wrongs must be corrected, yes? Why is the respect for debt more important than the respect for humanity?
> There is no need for me to consider the actions of others I had no control over in order to act morally.
What does this have to do with anything? Slavery is not a matter of "if you don't like it, don't do it", it was a positive right protected and enforced through the state's monopoly on violence. That's what law is. Likewise with the legacies of slavery. It's not mere morality, it's existential to civil society.
If the state passes legislation to fund reparations based on past harm, that is no different to any other appropriations spending. And yes, the choice to pass such legislation is largely based on morality since there was no prior legal obligation to do so... but so was not absolving themselves of that slave-owner debt. The UK Parliament is sovereign, it could have willed away that debt with a simple majority, but it chose not to for 200 years. That too is a decision based on morality, and a telling one: that humanity is less important than debts being paid.
> Nations are not individuals.
Nations are not literally individuals, but state personhood is a thing, akin to corporate personhood. I'm not entirely sure what your point is here.
> Similarly, individuals do not inherit debt.
You're doing the whole "don't therefore can't" thing again. I have a vague recollection of debt inheritance in history's past. 'We don't do that because we don't do that' is not an argument.