lol
good luck sticking them with the debt.
and the US government is never going to let all that land and the minerals that come with it go.
Well, I don’t see how the debt apportionment would be agreed upon prior to secession. The seceeding states would be stupid to take any “old” debt on. That is one of the reasons to leave.
And if the land you mentioned is in one of the seceeding states, the old US wouldn’t have a choice. If it is in the border it belongs to the seceeding state.
Of course, this assumes that the secession would work... Granted, a big assumption. These sorts of things would only be decided after the fact, not prior.