This really should be discussedon the N&Vs board. Hereare some figures that may interest you.
http://en.wikipedia.org/wiki/Union_Army
Ethnic groups
The 26th U.S. Colored Volunteer Infantry on parade, Camp William Penn, Pennsylvania, 1865.The Union Army was composed of many different ethnic groups, including large numbers of immigrants. About 25% of the white people who served in the Union Army were foreign-born.[5]
Breakdown of the approximately 2.2 million Union soldiers:
1 million (45.4% of all Union soldiers) native-born Americans of British ancestry.
516,000 (23.4%) Germans; about 216,000 were born in Germany.
210,000 (9.5%) African American. Half were freedmen who lived in the North, and half were ex-slaves or escaped slaves from the South. They served in more than 160 "colored" regiments. One such regiment, the 54th Massachusetts, is dramaticized in the film Glory. Others served under white officers in Federal regiments organized as the United States Colored Troops (USCT).[6]
200,000 (9.1%) Irish.
90,000 (4.1%) Dutch.
50,000 (2.3%) Canadian.
50,000 (2.3%) born in England.
40,000 (1.8%) French or French Canadian. About half were born in America, the other half in Quebec.
20,000 (0.9%) Scandinavian (Norwegian, Swedish, and Danish).
7,000 Italian
7,000 Jewish
6,000 Mexican
5,000 Polish (many of whom served in the Polish Legion of Brig. Gen. Włodzimierz Krzyżanowski)
4,000 Native Americans
Several hundred were: Hungarians, Portuguese, Chinese, Indians (born in India), and other nationalities.
Many immigrant soldiers formed their own regiments, such as the Irish Brigade (69th New York, 63rd New York, 88th New York, 28th Massachusetts, 116th Pennsylvania); the Swiss Rifles (15th Missouri); the Gardes Lafayette (55th New York); the Garibaldi Guard (39th New York); the Martinez Militia (1st New Mexico); the Polish Legion (58th New York); the German Rangers (52nd New York); the Highlander Regiment (79th New York); and the Scandinavian Regiment (15th Wisconsin). But for the most part, the foreign-born soldiers were scattered as individuals throughout units.
For comparison, the Confederate Army was not very diverse: 91% of Confederate soldiers were native born and only 9% were foreign-born, Irish being the largest group with others including Germans, French, Mexicans, and British. Some Southern propaganda compared foreign-born soldiers in the Union Army to the hated Hessians of the American Revolution.