Joseph Glatthaar's 2011 book of statistics (Soldiering in the Army of Northern Virginia: A Statistical Portrait of the Troops who Served under Robert E. Lee) states that foreign-born soldiers comprised 3.4 percent of the army. Some criticism has been leveled that his sample size is small, but my own research of Lee's army in mid-1863 is close to what Glatthaar reports. Some units exceeded the norm, such as the 8th Alabama regiment, which had both a German company (G) and an Irish company (I). Here are some estimated percentages of foreign born soldiers in Alabama infantry regiments:
8th Alabama - 21.15 %
9th Alabama - 7.08 %
15th Alabama - 1.95 %
11th Alabama - 1.52 %
I would like to learn of known foreign-born percentages in these and other units. I don't suppose attrition during the war would materially alter those percentages.
Of countries represented, Ireland, where the populace fled widespread famine due to the potato blight, contributed the largest number. Social upheavals in the Germanic states also brought large numbers to our shores, especially from Prussia. But others arrived from distant locations, like Private Thomas R. Morris of the 15th Alabama, who was born in New Zealand, and Private Larance Lewis of the 4th Alabama, a native of Sweden. Are there other atypical countries known? The Federal army at Gettysburg contained some Chinese, Russians, and so forth. In the southern army, Louisiana units appear to have the most diversity, with representatives from the West Indies, Malta, Alsace and Mexico, among others.
Foreigners were said to be less well off on average, although some came with military experience and achieved higher rank, despite the expected prejudices. For instance, Collett Leventhorpe, a former British army officer, became a Brigadier General of State troops in North Carolina. Who are the ranking foreign-born officers in the Alabama commands? I know of Captain John Cussons who was featured on this board (England, 4th Alabama); Major Adolph Proskauer (Prussian and Jewish, 12th Alabama); and Captain Frederick Fischer (German, 12th Alabama).