It depends -
You would only have to file a Canadian income tax return if you have certain types of income. Click this link for more information about what income causes you to have to file a Canadian tax return - https://turbotax.intuit.ca/tips/who-is-required-to-file-an-income-tax-return-126
Regarding your 1099-DIV and T5 NR4 - for your US income tax return, if you are considered a US resident then you will need to report all investment income from all sourced in USD on your US income tax return. If the amounts reported on your 1099-DIV are the same as what is being reported on your T5 NR4 then you will only have to report the income from the 1099-DIV on your US income tax return. You will be able to claim a foreign tax credit in the US for any Canadian taxes paid on income that is also being taxed in the the US.
