Leo Lucassen's The Immigrant Threat tackles the question of whether it is reasonable to believe that the integration process of these new immigrants will indeed be fundamentally different in the long run (over multiple generations) from ones experienced by similar immigrant groups in the past. For comparison, Lucassen focuses on large and problematic groups from western Europe's past (the Irish in the United Kingdom, the Poles in Germany, and the Italians in France) and demonstrates a number of structural similarities in the way migrants and their descendants integrated into these nation states. The book emphasizes that the geographic sources of the threat have changed and that contemporaries tend to over-emphasize the threat of each successive wave of immigrants, in part because the successfully incorporated immigrants of the past have become invisible in national histories.The book also includes a discussion of old and new migrants in the U.S.