Not only India. It’s even Western Europe - which is generally not a low cost area. US salaries for senior/principal levels are 3-5x of what the rate is there.
On a work visa you can only live so long in the US before you have to leave for one full year or morr. Greencard is a lottery, you aren't entitled to one.
I'm a Vancouverite who has worked in the US (flying to customer sites) for 15 years now. A coworker moved to the US, didn't get the Greencard lottery, had to move back.
That's wrong.
Other than that, the answer to "why don't Canadians drive 3 hours south" is "they do". The brain drain from Canadian tech is real.