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".
I am not a lawyer, but I think the 457 visa fills a role similar to the H1B or E3. You need to coming in for a job on the "Skilled Occupations List"[1], which currently includes various job titles related to software development.
Yes, but with the job market the way it is, it's not too risky.
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.
If you entered the US on a VWP, and try to reenter the US on the VWP without going further than Canada, Mexico or the Caribbean, you may find yourself denied entry.
I'm not sure if this applies if you were on a different class of visa before attempting to reenter the US using the VWP. I think the US border agents would be very suspicious though.
I've entered the US about 15 times since my E3 expired, and i'd say i've been specifically questioned about my E3 on 8 or 9 of those occasions. "You used to work in America? What's the name of your current employer? Are you looking for a job at the moment? You know you can't work in the US any more, right?" Stuff like that.
To be clear, I haven't had to deal with E3 related issues for 7 or 8 years and the subtle details of it have probably changed. Hopefully you never find yourself in a position where your E3 becomes invalid unexpectedly but if so, speak to a lawyer to find out the current gotchas and how US Immigration interprets the laws. (Or look at http://www.expatforum.com/expats/america-expat-forum-expats-... - it tends to be an excellent source of typically up to date information.)
Pro-tip for Australian's living in North America (or anyone crossing the Pacific, really): Qantas/OneWorld (and maybe other airlines) typically doesn't charge one penny extra if your North America <-> Australia route includes a stop in Hawaii. Hit up hotwire.com and find a cheap hotel in Waikiki and it's the absolute perfect way to break up a 14+ hour flight.
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".