Perhaps you're misunderstanding something here:
A > If a person or organization's actions were wrong, then morally (and at least in principle, legally) some kind of appropriate recompense is due to the person or organization wronged. You're not actually trying to dispute that, are you?
B > If someone dies, as a general rule the things they own - or the things they are owed - are passed on to their family and descendants. Granted there's sometimes technicalities, but are you going to dispute
that as a general rule?
So if the United States government rightfully owes some kind of recompense to the victims of its policies, such as those in support of manifest destiny, widespread dispossession of native American tribes, the trail of tears and so on, taking a century or more to acknowledge that debt doesn't make it not exist. From A and B, the debt is obviously owed to their heirs, where they can be identified.
Honestly, are you really trying to say that the policy you believe your and other governments should follow is just to deny any wrongdoing until the victims are dead, and then it suddenly doesn't matter any more? Maybe just cut out the middle step and kill people outright, because once they're dead nothing is owed to their heirs?