There are permissioned "blockchains" which are just private ledgers, that banks could use with permission from the US gov't. These can be anything from a centra

There are permissioned "blockchains" which are just private ledgers, that banks could use with permission from the US gov't. These can be anything from a centrally run DB with ACLs or something like Hyperledger with permissioned P2P access. Whether you call it a blockchain or a DB with ACLs is immaterial; it's still much cheaper, faster, and pleasant to use this system over the current system of complex intermediaries in the US. Europe seems to have solved this problem with SWIFT.