For example, in the case of a U.S. citizen returning to the States, you can get your Social Security Number fairly quickly (presuming you have a passport) - but if you're bringing along a spouse and/or children, you need to begin the paperwork of essentially sponsering them into the country and obtaining their green cards soon after they arrive/join you. That process can take years even though they rise up to the top of the priority list by being related to or immediate family of a U.S. citizen. And those family members should be prepared not to travel outside the U.S. once the application process is underway - or expect to apply for temporary travel visas or documents well in advance of any travel they might want to take.
Another thing (Denis), you as the returning U.S. citizen have to submit a minimum of your previous 3 years U.S. tax returns, presuming you haven't been filing in the States every year. That was something I learned...there's an expectation in the U.S. that you need to file every year no matter how long you've been out of the country or where you might live (whereas you can be a Canadian citizen and live elsewhere and are not expected to file Canuck tax returns each year). It's just a fairly substantial accounting and potential taxes owed cost to factor in.
For the rest of you looking for legal permanent residency, essentially you are wanting to obtain an employment related green card by getting sponsered as an alien of extraordinary ability. From one of the zillion websites that discuss this process:
Getting an employment related green card is generally one of the best options available. It is important to note that the time it takes to process employment based green cards can range quite a bit. It is possible for EB-1 and EB-5 applications to be approved in less than a year. EB-3 applications on the other hand can take five years or more. These are the five types of employment related green cards to consider:
EB-1: This is for aliens with extraordinary ability such as researchers, outstanding professors or multinational business executives or managers.
EB-2: This is for aliens with advanced degrees who have an employer or sponsor or aliens with exceptional ability.
EB-3: This option is for unskilled workers with an employer or sponsor, skilled workers and professional workers with a university degree.
EB-4: This is available for religious workers
EB-5: This is an option for aliens who are able to invest $1,000,000 and create at least ten new full time jobs. It is also possible in certain limited situations that an investment of $500,000, if it creates at least five new jobs, may be acceptable.
First order of business, get an immigration lawyer. The paperwork is mountainous and there are oodles of little ways to get tripped up...or be considered a low priority and stuck at the bottom of the pile (and believe me, it's a tall pile). Getting work on a tv show/movie or with a company is usually the next order of business, but I know of some colleagues who were essentially sponsered by their U.S. agent (the agent acting as employer and making a case for the promise of work). Adjustment of Status is another option that comes up (more for spouses or children of citizens or green card holders), but better to hear a lawyer explain that one.
Anyway, it's a long haul undertaking - and if it's something you're seriously considering, start looking into it now.
SONG & ARTIST? - "It's not easy being green
Having to spend each day
The color of the leaves
When I think it could be nicer being red,
Or yellow, or gold
Or something much more colorful like that"