Anecdotally, a lot of us return to Canada after a short stint in the US.
Speaking as a Waterloo grad that moved to the US for about 5 years post graduation. Many of my university classmates did something similar.
I worked in the US for a bit when I started out. I paid more income tax in CT than in Toronto on the same salary.
I just wanted to come back home. Even in small town CT, there were areas we were told to stay away from after dark.
Although it feels like all of the desirable jobs (in terms of technical interestingness and pay) are in the US. At least for internships.
1) more interesting work opportunities; and
2) more money
And the delta on (1) has never been smaller thanks to remote work post-covid (even after all the RTO).
So basically, at some point, you start asking if the extra money is worth it.
(Depending where you come from in Canada, lifestyle in SF might be better overall - but then you can just move back to somewhere else in Canada and have it all.)
But eventually life catches up to you, especially if you have strong family/social roots in Canada. It's not easy to bootstrap that in a new country.
I was also there under a TN Visa and had a few border experiences that rubbed me the wrong way since the TN Visa is a bit hand wavy and up to the border guard at your time of entry. The hostility at times from the border guards didn't make it feel like I was returning "home". Sure, I worked for a company that had an army of lawyers to fix it if anything went wrong but it still leaves you with a sour taste. I can't imagine they're getting any friendlier these days.
Lastly, I didn't mean it like 5 is some magic number - some stay less, some stay more.