Not sure about Toronto, but from my anecdotal observation, people come to Vancouver because it's awesome, not because they couldn't get into the US. At least, I've never heard a single coworker say anything along the lines of "I wanted to work in [anywhere in US], but couldn't, so I came to Vancouver".

Don't forget about all the people waiting for their L-1.

(I've been in that boat myself, and every single person I worked with in the office in Canada is in US today.)

This is accurate.

Source: Canadian working in FAANG in Canada