Tom,
Very interesting stats that you have turned up.
The crux of the argument is for native born CS soldiers many of whom came from long established English families in America based on the refutation of the Celtic/Scots heritage of Southern troops.
James Willis wrote a fine book on Arkansas soldiers in the Western CSA and noted that something like 80 plus per cent of them were not born in Arkansas. I understand that the figure for Texas troops is in the same ballpark.
Greg Biggs