Short answers, pulled from the story.
Over one-tenth of all Americans were foreign-born by 1860, swelling the population from five million to roughly thirty-one million people. Approximately two-thirds of all Americans lived in Union-controlled territory where ninety-one percent of pre-war immigrants resided.
Major General Franz Sigel held the rank of major general and became the highest ranking German American officer in the Union Army. President Lincoln appointed him after he served as a veteran of the 1848 revolutions.
Union Major-General Ulysses S Grant issued General Order No. 11 which expelled all Jews from his military district to reduce corruption. President Lincoln countermanded this controversial order almost immediately after learning about it.
Major-General Camille Armand Jules Marie de Polignac commanded a volunteer division comprised of descendants of various European communities living in Louisiana. He achieved victory at the Battle of Mansfield during the Red River Campaign.
Approximately forty thousand Irishmen joined the ranks of the Confederate Army. Most foreign-born Confederate soldiers had spent their lives in the American South and fought out of personal affinity to their local community rather than support for slavery.