Transfer our US tenant to AUS tenant

How can we transfer our US tenant user to our AUS tenant? Both are under the same account.

As stated in the data transfer policy the transfer of data from one tenant/account to another is something that is currently not supported:

At this time, Auth0 will not transfer data from one Auth0 account to another.

It’s possible for you to transfer some of the data yourself using the Management API as noted in the linked policy, however, depending on your exact situation this may or may not meet your requirements.