Step 1. Create a NEW account through your PS3/PS4. When it asks for address information insert an American address (I'd use Oregon). You'll need to use a separate e-mail address (obviously, a simple Gmail account does the trick).
Step 2. Make it one of the active/master (whatever it is called) accounts (both accounts (US + AU accounts) can be master accounts concurrently).
Step 3. If you want to have PS+ on it then you'll have to purchase PSN cards (either monetary ones or straight PS+ for X months cards) through a store such as Amazon (again use a US address, Oregon avoids state sales taxes).
Step 4: Redeem those codes online (Playstation's online store) or on the Playstation itself (make sure your US account is logged in).
This will allow you to download the American WWE Network app on Playstation account (you'll also be able to get PS+ games from both your pre-existing Australian and new American PS+ accounts (again a lot of value in doing this).
As for needing an American credit card with the WWE who knows. However, there are ways around this such as an online purchase of a preloaded VISA card.
It's about 15-20 minutes work and you're laughing.
How do you go about the US credit card? It looks like you will need to subscribe a credit card for the network and not use PS+ credit.
Also, is it essential to subscribe to PS+?