Some of it was beneficial both for Americans and the Mexican workers. But much of it really wasn't. The treatment of the Mexican people by Americans in the southern states in the 40's and 50's was unconscionable and indefensible. The illegals here now are treated royally by comparison.
Beyond that fact and from a more practical point of view, the USA population in 1950 was about half what it is now and far less of the farm and ranchland was automated as it is now. The illegal Mexcan workers then were actually needed and weren't displacing that many American workers.
These days they do. Now more than 50 years later, our population has doubled and different dynamics apply.
It's sort of like comparing the original USA immigration policies with those necessary after the vast empty areas of America started filling up and there was less and less land, and therefore less work for the newcomers. When we reached the tipping point where too many new immigrants could no longer be assimilated into the existing American culture, it was necessary to establish quotas.
Each era has its own set of problems to deal with. Certain principles and values from the beginning are as valid today as they have ever been. But the issues of jobs, population densities, and other components of our culture do change over the years and bring their own challenges.
