I am a US Resident who worked for roughly 5 months in Canada in 2016. I have a T4 tax form, but no W2. I have no idea how I'm supposed to file my US taxes.

This is obviously foreign income without a Form W-2 (see the attached sample screenshot). We can't "translate" your T4 into a Form W-2, so you will have to do that as you enter it in TurboTax.

First, enter your foreign income.  

https://ttlc.intuit.com/replies/6022142

If you paid foreign tax on any of this income, 

https://ttlc.intuit.com/replies/6017167