Earlier quoted context omitted.
I'm Australian. We have a special visa, the E3, which is very easy to get. Meanwhile almost everyone else is stuck in the H1B shitshow, which has in the past 5 years grown from merely "terrible" to "nuclear-powered self-propelling toxic thunderblob".
Does the E3 still have the "if you lose your job you have 2 weeks to leave the country" clause on it? It had me on edge the whole time I was in the States (which funnily enough prompted me to find a job in Toronto).
Here's how it would play out if I left my job.
I'd fly to Toronto on Canada's visa waiver, wait there until the E3 expired.
Fly back to NYC on the USA's visa waiver program. This gives me 90 days to find an employer who will sponsor an E3.
Fly back to Toronto to get the E3 done.
Fly back to NYC to start the job.
It'd be a silly shuffle of about a month, and more disruptive and expensive than it would be for someone holding a green card or citizenship. But in no sense would it be a game-over disaster.