Why the Employment letter
> That being said, I was asked for an employment letter at my CP > interview. Since I had one on hand, I did not argue the finer
> points of this issue.
And quite appropriately.
Completely regardless of the underlying basis establishing
an immigrant visa eligibility, any immigrant must demonstrate
that he is able of supporting himself and dependents, if any, in the US, and would not likely become a "public charge".
The most common (though not the only) means by which EB immigrants demonstrate this is a continued US employment. Aside from that, EA immigrants are required to "intend to continue practicing in the field of endeavor in which their extraordinary ability is recognized". On occasion, INS has
construed a failure to keep a job in the field as contravening this requirement.