You can file a tax return using TurboTax from anywhere in the world where you have an internet connection.

The TurboTax desktop CD/Download editions for tax year 2017 are available for purchase at this website - https://turbotax.intuit.com/personal-taxes/cd-download/

The TurboTax online editions for tax year 2017 will be available in early December.

You will need a US credit card with a US billing address to purchase the TurboTax software and services from the TurboTax website.

Go to this IRS website for general information on taxpayers living/working abroad - <a rel="nofollow" target="_blank" href="https://www.irs.gov/individuals/international-taxpayers/taxpayers-living-abroad">https://www.irs.gov...>
For specific information review IRS Publication 54, Tax Guide for U.S. Citizens and Resident Aliens Abroad - <a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/p54.pdf">https://www.irs.gov/pub/irs-pdf/p54.pdf</a>

That's tricky.  You can't pay for Turbotax Online using a foreign credit card.  It should work if you keep a US credit card active.  If you don't have a US credit card but do have a US bank account, you can pay for Turbotax Online from the bank account by contacting customer support.  You will also need a US bank account to receive your refunds by direct deposit or pay the tax you owe by direct debit.

For Turbotax desktop version, purchased as a CD or download and installed on your own computer, you would need a US credit card to buy the program direct from Turbotax.  You might be able to purchase a CD from Amazon or another retailer using a foreign credit card, but I have heard there are restrictions on shipping Turbotax to foreign countries (I have not tested this).  Or you could get a friend in the US to buy the program for you and send you the installer CD by mail, or send you the downloable installer file by Dropbox or Google Drive or a similar service.

I see you are writing from Mac OS 10.12.  Don't upgrade to High Sierra yet, Turbotax still has some compatibility problems.