Earlier quoted context omitted.
I don't see why these would need a blockchain rather than just a centralized database. I'm very skeptical of these use cases.
The purpose of blockchain is to solve what happens when neither side of a transaction trust the other. For example, suppose US and Iran agreed to pay each other some amount as proof of their sactions deal... US doesn't trust Iran or its central bank. Iran doesn't trust SWIFT, since it can be easily manipulated by its enemies (as it has been, before). US doesn't trust the alternative to SWIFT, since it is run by Russi…
Normally the courts solve this problem, so this is only an issue if one or both parties are operating outside of the law.
Which, for normal financial enterprises trying to do business, creates regulatory problems: Chase can't exactly transact with the PLA without getting bulldozed by regulators, and you can't exactly hide the transaction on blockchain (since its immutable).
In the scenario you describe, there are ways of cheating even in blockchain (51% attack), and there are ways of solving the issue outside of blockchain (military force, embargos).