Question

why was the 1924 National Origins Act considered irrational and inconsistent with core American principles by 1965 when lawmakers overturned it?

Answer 1

The immigration act 1924 (Hart-Cellar Act) was to enable the United States government to execute power to limit the number of immigrants or non-northern Europeans to enter into the U.S. This limitation aimed at limiting the number of Europeans and Asians entering the country. Later, in 1965the act was modified since it did not honor American Core principles which were; liberty, equality, unity, and diversity.
In removing the racial and national barriers the Immigrant act would alter the demographic mix in the United States.