17 year old trying to get back to US, with dual citizenship in Australia

There are currently restrictions in place for Australians (including dual citizens) leaving the country.

https://covid19.homeaffairs.gov.au/leaving-australia#toc-1

If you are an Australian citizen or a permanent resident you cannot leave Australia due to COVID-19 restrictions unless you have an exemption. You can apply online but you must meet at least one of the following:

• your travel is as part of the response to the COVID-19 outbreak, including the provision of aid
• your travel is essential for the conduct of critical industries and business (including export and import industries)
• you are travelling to receive urgent medical treatment that is not available in Australia
• you are travelling on urgent and unavoidable personal business
• you are travelling on compassionate or humanitarian grounds
• your travel is in the national interest.

An exemption may apply if you aren't normally resident in Australia.

You are considered ordinarily resident in a country other than Australia if international movement records show that you’ve spent more time outside Australia than inside for the last 12 to 24 months. You do not need to carry a paper record of your movements with you. If required, Australian Border Force officers at airports can check your movement records in Departmental systems.

If you have not spent more time outside Australia than inside for the last 12 to 24 months, but still consider yourself to be ordinarily resident in another country, you can submit a request for a travel exemption.

My kids have frequently traveled to the US on their own when they where minors without any type of special paperwork. No one ever asked for a travel permit or Guardian consent form.

However there are a few caveats

1. You need a to book a flight and someone needs to pay for it. The ticket must be in your name and you may have to prove that the booking is legit, which in some cases requires you to present the credit card used to buy the ticket at check in. Rules vary a lot between different airlines.
2. Some airlines may require a guardian consent form. Check with the airline, rules vary a lot.
3. You need a valid US passport. No airline will allow you to board a US bound flight without a valid US passport.
4. You may get snagged in exit control if your name shows up in the system as "reported missing" or "run-away", i.e. if your parents/guardians reported you to the authorities for one reason or another.
5. On the customs form you need to provide the address you will be staying in the US. For a minor they may a look a little closer whether that address makes sense.
6. You will get interviewed when you enter the US. They may ask you why you are travelling, where you are going, what you will be doing, where you will be staying etc. As a US citizen, they can't deny you entry but they may alert social services if they don't like the answers.

Obviously by far the safest choice here is to get agreement and permission from at least one guardian or parent. If that's not possible, you may want to reach out for help locally. Travelling adds to the complications.