Actually, only physical cash is what you can spend immediately. If you pay by card, the card issuer promises to pay the company within 3 days of the transaction but the funds are just somewhere between your two accounts and are pending in both so that's not very instant (when compared with an average for bitcoin of 10-30 minutes).
As was mentioned above, there's the lightning network where transactions normally take less than 10 seconds to go through (they just use contracts in the wallets thst can be broadcast to the blockchain at any point to redeem the btc owned by that node).
actually LN is not settled in 10 seconds. its in millisat "payments" which are not settled. and usually the funding transaction has a lock for multiple blocks meaning it wont settle quickly either. LN's promotion is that people dont need to settle after a week or month, they can just renegotiate their channel millisat balance to 'rebalance' the channels without ever having to settle