From the linked site:
Prior to 1965 the United States was roughly 90% White. That year the immigration laws were changed which had prevented non-Western immigration that would alter the demographic makeup of the population. It’s important to note that US President Johnson, who signed the new immigration changes into law, promised the people (who largely opposed the changes) that the bill was ‘not revolutionary.’ Ted Kennedy, one of the key Congressional figures in getting the new immigration law passed, promised the people that the demographics of the United States would not be changed.
Of coarse Kennedy and Johnson were Lying!