Not my area of expertise, but Americans took a very negative view of immigration in the 1920s. The [edit] Emergency Quota Act of 1921 and the Immigration Act of 1924 effectively ended decades of somewhat restriction-free immigration to the United States, such that from the 1920s to the end of WWII immigration basically drops off to nothing and effectively doesn't return to pre-1924 levels until the 1960s.

There are a few proposed reasons for that that I'm familiar with. One is that the number of foreign-born residents both in absolute terms and as a proportion of the population peaked in the 1920s after several decades of a sustained high level. The US has not reached a similar proportion until today (which perhaps makes it historically unsurprising that there are growing calls to restrict immigration, but I digress).

Secondly was the perceived chaos of the mass migrant movements in the aftermath of WWI that Americans just wanted nothing to do with. By way of example this can be seen in the debates over American approval for the Balfour declaration, in which it's made quite clear by the people testifying in favor of the declaration that the US should support the creation of a Jewish national home in Palestine as an alternative to continued Jewish migration from eastern Europe to the United States.