So, how many mexicans and venezuelans fought in our civil war?  Let me type very slowly....Americans fought on both sides.   Americans died, were wounded, on both sides.  Those in the south fought for the Confederate States of AMERICA.  Ignorant people call the Battle Flag the "Confederate Flag"...there were several Southern Armies, each with their own Battle Flag.  All of them Americans.  
As to blacks fighting for the south, I refer you to search Google:  Walter Williams, professor at George Mason University, Syndicated columnist and nationally known speaker.  Oh, yeah...he's black.  There are many sources describing blacks fighting for the South, including the likes of Horace Greeley.  You appear to be deficient in your historical knowledge of the War of the Rebellion.