The US region that has a population that is most likely to be dominated by people of Irish, Italian, Puerto Rican and African American backgrounds is c) the Northeast. This is because large swathes of immigrants moved to New York City. Many Irish immigrants moved to New York during the Great Famine, while many Italian immigrants moved from Southern Italy where there was a lack of job opportunities and the same goes for Puerto Rican immigrants. African Americans came in large numbers when they were freed from slavery after the Civil War.