My understanding is that Canadian FAANG offices are staffed mostly with those who cannot (and often will never get) a US visa, plus the odd local who doesn't want to move to the US for personal or family reasons.
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".
