Any employee can change the ledger at a bank.

Bank ledgers account for value, but do not hold that value.

Immutability. Decentralized persistence and accountability (this isn’t true of all blockchains necessarily, but it is of Bitcoin). Publicly accessible.

'Blockchain' is a rather generic buzzword at this point. It isn't entirely clear what it means in this context. Creating a blockchain is easy at this point, but a blockchain alone isn't really anything that special.

Bitcoin is quite different than a banking ledger though, in that it allows for a censorship resistant method to account for native digital assets.