During the late 19th century, the United States experienced a significant influx of immigrants, particularly from Southern and Eastern Europe. This wave of immigration was driven by various factors including economic opportunities, political unrest, and social issues in the immigrants' home countries. However, the reception of these immigrants was not universally welcoming, leading to the establishment of various policies and social movements aimed at regulating immigration.

Which of the following statements BEST represents the primary concern of nativist movements during this period?