That was the effect that JFK was looking for in the his legislation that was passed after his death, in 1965, to replace the American WASP voters with Catholics and non-WASPs.
JFK (and the left) wanted to import democrat voters to replace Protestants, who had only voted democrat twice before JFKs death, 1932 and 1936, and a group who has only voted democrat once since his death, that was in 1964.
When the history of the US is written, historians will point to the 1965 Immigration Act as the primary cause of the decline and fall of the United States of America. We are in decline now and it will only get worse.