I suppose you know that 'legal status' is a very broad term - and not the same like citizenship in this context. Your 'legal status' as an immigrant could depend on the fact that you are employed, it could even be tight to an employer, profession or industry.
You think immigrants 'are sending their money back to Mexico' ? Time Magazine reports that "some 80% of what undocumented workers earn in the US stays in the US". (Issue April 10th, 2006 - Page 43)
Also, the 'small amount' you refer to, that would something like $4 Billon that illegal immigrants contribute to the North Carolina economy in 2004 (according to a study of the University of North Carolina).
Alex