I agree. That my take, also.
The America of the 1840s at least had a frontier to settle. Many more immigrants could be accepted in the growing country and out West. And if native-born went West, the places they left behind were not so crowded.
By the early 1900s this had changed. The frontier was settled, and America on the east coast and in the Midwest was filling up with two many people. The horror and shock of WWI and the refuge crisis it caused was a huge problem for the country as it appeared that everyone would come to America. By 1919 1/3 of all Americans foreign-born. Congress passed the Immigration Act of 1020, that put a stop to most immigration.
This resulted in the “Americanization” of the vast horde of foreigners and was good for them and the rest of the country.
Ted Kennedy got mass immigration started again with his new Immigration Act of 1965, but this one forced the government to let it people from everywhere, not just Europe.
NOW we have as many foreign-born or MORE than we did in 1919 and we really need to have another hiatus.
1920, not 1020!