score:2
US embassy in the UK says this:
If I enter the United States visa free under the Visa Waiver Program, can I then travel to Canada/Mexico/ Bermuda or the islands in the Caribbean?
Yes, provided you have a return or onward ticket. If your return journey will take you back through the United States, even if only in transit, the total trip, including both periods of time spent in the United States/Canada/Mexico Bermuda, or the islands in the Caribbean cannot exceed 90 days. If it does, you will require a visa.
From the USA Governments travel website it states this:
If you are admitted to the United States under the VWP, you may take a short trip to Canada, Mexico, or a nearby island and generally be readmitted to the United States under the VWP for the remainder of the original 90 days granted upon your initial arrival in the United States. Therefore, the length of time of your total stay, including the short trip, must be 90 days or less.
So the main government travel website only takes about readmission for short stays in nearby countries and islands. The answers are quite conflicting, and conflicting with what the Australian US embassy says.
Update 9th February 2018
I emailed U.S. Customs and Border Protection and got this response.
Response Via Email (CBP Officer) 02/09/2018 06:14 AM
Hello, We recommend that you apply for a visa if your trip to Canada/Mexico/ Bermuda or the islands in the Caribbean exceeds 90 days.
Regards, ESTA Team
Looks like it's best to get a visa, this comes directly from a CBP officer.