How, pray tell, would a cryptocurrency help here? You have all the crypto disadvantages (either untested or slow or scams or boiling the planet...) plus the same issue with adoption. We already have banks and they already have bank accounts. We have SWIFT, SEPA, etc. They know how to talk to each other. Get them to modify an existing protocol or make a new one for microtransactions.
It's a super hard task but with crypto you still have that super hard task (adoption) plus crypto itself (a million drawbacks).
It's not scientific and it's not engineering.
You solve a problem with the simplest equivalent solution, no more.
Crypto is like God. It gets sprinkled over every discussion. There's a reason science doesn't go: "A equals B plus God" to prove anything.
The one most people use. SWIFT.
And yeah, blah blah sanctions, Russia, Iran, like most of the world's business is happening there and like the crypto Ponzi schemers really care about the "under-banked".