US taxes its citizens/residents ( green card holder or aliens whom have met the substantial presence test ) on world income and gives credit for taxes paid to another country.
So you have to file US return covering only US income ( if you had not the substantial presence during 2018) or world income if you had become a resident / resident for tax purposes.
Equally you will need to file a Canadian tax return per Canada's tax laws.
TurboTax prepares only 1040 series returns ( US citizens/ residents/ residents for tax purposes ) and not 1040-NR series ( Non-resident alien with US income).
TurboTax will ask questions about treaties but s generally not geared towards raising and resolving treaty issues / conditions ---- this is generally aimed at US taxpayers with generally US sourced income. It work pretty well for US taxpayers whom are expats.
Is there something else I can help you with?
