The fact that real world energy is expended is the thermodynamic guarantee of the irreversibility of a transaction.
If you have access to the VISA database, and change something, you cannot have the cryptographic proof that it has not been tampered with. At the very best, you trust a VISA root key.
With Bitcoin you trust math and physics, telling that if the whole network has expended 1TWh after my transaction, at least twice that energy will be necessary to reverse it, and the only data i need to prove that, is the blockchain.