TurboTax doesn't support non-resident tax returns. If you are filing as a US citizen living abroad then you will need a US address and you will file a regular 1040 and take a deduction for any foreign taxes that you pay or take a credit for foreign earned income using form 2555.
If you are filing as a resident of Canada and a dual citizen then TurboTax partners with Sprintax and you can use them to file a form 1040NR.
Thanks for your quick response. Just to clarify: technically I am a US citizen living abroad *and* a Permanent Resident of Canada. But it sounds like I need to choose one or the other?
To clarify, the IRS states that if you are a U.S. citizen or resident living or traveling outside the United States, you generally are required to file income tax returns, estate tax returns, and gift tax returns and pay estimated tax in the same way as those residing in the United States. This means filing a 1040 resident return and reporting your world-wide income
If you give up your US citizen status and become a citizen in Canada, then you would file a 1040 NR return and just report your US income if you have any.