All a crypto currency would do is provide another payment method when the foreign government does decide to pay (and is not engaging in a trade war)
You are familiar with crypto currency basics, yes?
In addition to another payment method, it is also a better payment method.
Some of the more applicable merits include.
Proof of funds
Validated low friction escrows
Smart contracting
This could provide contract enforcement for order cancellations.
Cancel an order and still pay some %. Manufacturer still has the goods and can sell, and also receives compensation for unfair business practice.
Folks whine about not having consumer protections, but they are there for anyone that wants to use them, what is missing isn't the protection, its just missing the protection racket.
I'm no expert in ex-im bank stuff, but these things just seem to be such obviously better mechanisms for solving the problems. Save the big guns for when they are absolutely needed. State department has enough to worry about.