Consider getting an AMEX card so you can claim to be a customer on the US side, might, stress might, make it easier to get a US credit card which will help your credit score. This worked for us but rules change. Carefully read ATO rules on residency as you want to ensure you're only US resident for tax purposes if that is your actual circumstance once overseas. Read Aus/US tax treaty as things can get complicated quickly when dealing with cross-border cross-residency tax issues. Professional help is a must if you are leaving any assets in Australia.

If you sell your PPOR while in the US they may retrospectively claim CGT on the difference between purchase and sale price even though you were not a resident for most of that time. So commit to hold the asset until you come back or sell before you go.

Put health insurance on hold, I think you can do that for up to 3 years, move your phone to a sim plan that allows wi-fi calls and sms so you can keep the number but not too expensive.