I’m in between radio interviews, so let me jump in here. I put the title above in quotes because the phrase “A Nation of Immigrants” really came into widespread usage because it was the title of Jack Kennedy’s propaganda book pushing his legislation to end the old quota system. It was written in 1958 to promote then-Sen. John Kennedy’s immigration changes, and republished in revised form after JFK’s death as part of the campaign to pass what became the 1965 Hart-Celler Act, which kick-started the immigration mess we’re still dealing with. Now, it’s not like I’m against policy books — I’ve got one of my own coming out early next year. But the phrase has been an explicitly political one from the very beginning, specifically designed to promote the passage of particular pieces of legislation in Congress. And Ted Kennedy announced a reissuance of the book just last month as part of the latest legislative effort to erode America’s borders.

See here for a little history:

In the 1920s and 1930s, neither historians nor sociologists of immigration used the term “nation of immigrants.” First used by a former missionary in 1882, picked up occasionally in the 1910s and 1920s by a mixed group of businessmen, critics of immigration restriction, and the occasional scholar, the idea of the United States as a “nation of immigrants” did not really capture the American imagination until the early 1950s, when immigration had waned to its nadir and when the scholarly study of immigration by historians and sociologists had practically ceased.
The popularity of this phrase — still heard in contemporary debates — was the product of another great debate about immigration. In his efforts to prevent Congress from including in the 1952 McCarran-Walter Act the discriminatory national origins quotas introduced in the 1920s, Harry S. Truman began asserting that the United States was and always had been a nation of immigrants.