By 1970 many of us were already being pushed out of jobs and housing by mexicans, I would say that Democrat policies were the most harmful and that most of the blame has to go to the Catholics that voted Democrat and gave us the Kennedys.
With no Kennedys, then we would still be America.
But there was no flood of immigration that early. The first hint of what was going on can be seen the census figures of 1980. Until about that time, migration was largely limited to the border states.