Isn't the global banking system basically a blockchain as well?
Basically there is a very large number of globally distributed nodes (banks) that transact with each other and that keeps a vee of their own ledger and they settle it every day or every couple of days to reconcile all the amounts. Yes not every bank has every transaction or every account balance but only those of their customers, but still, its distributed, decentralized, chained (though not cryptographically). So the only difference to btc is that btc has one ledger with everything, it is cryptographically verifiable (so it's trust less) and its faster.
OK arguably the banks are actually the layer 2 and clearing houses of the swift system are the layer 1 (which is more centralised than the banking system).
Assuming the above is true then maybe a better way to explain btc is not by explaining the tech and blockchain etc but rather by saying something like btc is like an alternative to the swift system and its clearing houses that is decentralized, open, and not controlled by any one entity, it is faster and fully transparent.
And if we say that, then the question comes - do "the powers that be" actually want competition in this manner... (not that they can stop it per se but they can outlaw it just like files haring cannot be stopped but be outlawed or made very inconvenient).
Just trying to think of the appropriate analogy that btc is better than...