Final answer:
The fervent anti-immigrant sentiment in the 1920s was driven by economic factors, cultural and racial prejudices, and fear of political radicalism.
Step-by-step explanation:
The fervent anti-immigrant sentiment in the 1920s can be attributed to a combination of economic factors, cultural and racial prejudices, and fear of political radicalism. First, economic factors and job competition played a significant role as immigrants were seen as a threat to American workers, with fears of job scarcity and wage depression.
Second, cultural and racial prejudices fueled the sentiment as many Americans held discriminatory views against immigrants from different ethnic backgrounds. Lastly, the fear of political radicalism, particularly due to the Red Scare and concerns over communist influence, led to increased hostility towards immigrants.