Upvote:2
If you're currently in the United States, traveling to Canada, Mexico, or the Caribbean will not allow you to stay longer in the USA. According to the US embassy in Australia.
You cannot extend the time on the Visa Waiver Program. The 90 days also includes any time spent in Canada, Mexico and adjacent Islands. Therefore, you cannot cross the border into these areas and then return for another 90 days.
Adjacent islands are defined according to ICE as
Your best bet would be to return to Australia or visit a country on another continent. However, you would not be guaranteed entry back into the United States and you will likely be questioned about returning to the US so soon.
If you stayed more than 90 days in the first place, your ESTA would be revoked and you would need to apply for a visitor visa. It may be challenging to prove that you will not overstay in the future.
[3] https://www.alllaw.com/articles/nolo/us-immigration/can-visa-overstay-be-forgiven.html
Upvote:4
Neither Canada nor Mexico nor the Caribbean will work. The VWP rules specify that if you go there and return (except if you're resident in one of those places) it will not change your original "admitted until" date.
For a "visa run" you need to leave North America.
(And even if you do so, it will most likely be difficult to convince the border guards when you reenter that the true purpose of your visit is one that is allowed under the VWP).