Incorrect. Green card holders (i.e., US permanent residents, but non-citizens) do not face "immediate deportation" if they change jobs.
By contrast Canadian permanent residents are treated exactly the same as citizens - except you can't vote in federal elections. Although with the choices on offer that's probably a blessing !
Especially one return from a conference where the minimum-wage-moron on passport control didn't understand the concept of visas (to be fair he had a limited understanding of the concept of passports or even other countries) and allowed me in for 24 hours which I spent queuing at LA's delightful immigration office downtown.
Still, well done to him for protecting the USA from another foreign Caltech physics prof.
(Not that I disagree that the whole setup is ridiculous and probably doesn't meaningfully add to security.)