What role did the idea of American exceptionalism play in shaping immigration policy?

The concept of American exceptionalism, which posits that the United States is inherently different from other nations due to its unique history, values, and political system, significantly influenced immigration policy by justifying the exclusion of certain immigrant groups. Advocates of this idea often claimed that the United States had a distinct identity that needed to be preserved, leading to policies that targeted specific nationalities and ethnicities deemed undesirable or incompatible with American values.

During certain periods, such as the early 20th century, this belief was used to rationalize restrictive immigration laws, such as the Immigration Act of 1924, which established quotas that favored immigrants from Northern and Western Europe while severely limiting those from Southern and Eastern Europe, Asia, and other regions. This was driven by a perceived need to maintain a homogeneous American culture, which supporters of American exceptionalism believed was under threat from these "less assimilable" immigrant groups. Thus, belief in American exceptionalism not only shaped views about cultural superiority but also directly impacted legislative efforts to manage the flow and composition of immigrants coming to the United States.