Canadians can enter the country for 6 months without a visa. This makes it is easy to work illegally for people who are willing to take that risk.
There is the TN visa, which is easy to obtain. But it's only for 8 specific professions. I for one worked as a Computer Systems Analyst. A job title I never heard before that. Once you have this visa it's bound to your employment, when you loose your job, you have to leave the country in 10 days. This is a temporary visa and you can not apply for a green card.
Then there is H1B. This visa allows you to apply for a green card, but you can only apply for it on one specific date per year, if you can get it depends on a lottery (!), which decides if you can work 6 month later. Also it requires a mountain of paperwork, which however the companies lawyer will normally take care of. From there it takes 2-3 year to get a green card.
I am waiting 8 months to renew my Swiss residence permit (I have to do it every year), despite that I live in Switzerland for 9 years already.
I guess you'd need limitations on health care and an awareness campaign about it (so that confused people didn't travel in an attempt to save money), but other than that, I think the only stopper is the slightly higher level of paranoia the U.S. shows towards foreign visitors.
AFTER EDIT: I am sincerely interested, and I think "hell" may be a bit of an exaggeration, so I'm not sure what's objectionable about this question. But let me know if you have an objection, okay?