Can you send Apple Pay Cash from the United States to Australia?

works at a vendor yes. It is possible it would work to send family members money IF they were Americans who have Apple Cash set up just visiting Australia. If they are Australian, Apple Cash is only available in the USA. You can use Zelle though which is integrated through several banking apps.

Yes, if Apple Pay is supported and they accept Discover also, you can use it as a payment method for Apple Pay. You cannot use it as a person to person payment in Australia.