[Ditto]

In answer to your question, because it is hard to immigrate to the South thru a BLOCKADE!

Long before the war, the vast majority of immigrants did not head to southern states.

How come?

[TexConfederate1861]

Probably because the South was primarily agricultural.
But as I said, there were lots of Irish & Germans in the South.

"Long before the war, the vast majority of immigrants did not head to southern states."

Source, please.