Can you delete a text message sent on iPhone before the other person reads it?

Nope. Once it's sent, it's sent.
Text messages are sent in seconds. The moment you hit send, the message is blasted into space by network antennas, then reflected back to Earth towards the phone thereceiversnumber is assigned to. All this is done within 2-6 seconds of hitting 'Send', so even if there was a cancel button, you'd never press it in time.