Well I'm by no means an economy expert or anything, I just wanted to point out that it's not as simple as "Keep the money in America!". There are always consequences to decisions like these.
I will say though that minimum wage increased are usually not all that substantial. $.50 here, $1 there. I wouldn't expect companies to react too much from chances like that. However, the cost of labor for people employing illegals would generally be very significant (depending on just how much lower than the minimum wage they're being paid). I don't think using minimum wage increases as a model would be a very accurate representation of what the effect would be.