[shoo]

check out: https://en.wikipedia.org/wiki/List_of_IT_consulting_firms

I'm not familiar with how this works in the US, but have seen a similar thing in Australia. IT outsourcing firm wins a contract with some big client (bank, telco, etc) to do some IT work. Fly in their "consultants" to design/build/run the systems from offshore, work them hard, bill them out to the client at some multiple of what they pay their staff. As a consultant, if you're lucky enough to get allocated to a project in a country you want to migrate to, you hope that the contract lasts long enough to let you apply for some kind of skilled worker visa. While you're working on the contract you're only legally able to stay in the country through your employer, so you have very little power to quit or push for a better deal if the working conditions or pay are bad. If you're lucky enough for the contract to run long enough and your visa to remain and work in the country comes through, then you're able to decouple from being a serf of the consulting company and can quit and get a better job with a local company, etc.

Anecdotally you hear of situations where someone is 95% of the way through the process to become a permanent resident of a country, then their employer loses their contract with the big client and everyone is sent back to HQ.