He was talking about ethnically German or Irish or even Swedish people mixing in with the founding British stock of the nation. Context matters. The founding fathers were extremely racist and xenophobic compared to just about every white American today.
If Ted Kennedy didn't change the immigration policy of this country, we would look largely the same today as what we looked like before he changed it(most likely even more European than we were, because we would simply increase the birth rate to make up for the lower immigration from Europe).
Luckily we are not so ignorant as to think all other races are inferior.
As for how we looked before Kennedy changed the laws, you are sadly mistaken. During WWII there were around 117,000 people of Japanese descent put into internment camps. That does not even count the people of Chinese, Korean, or other Asian descent. There were almost a million Asian Americans in 1960. That was 5 years before Kennedy changed the immigration laws. They were already here.
And Asians have always been the part of the population that is not white, but also doesn't seem to be a problem. In fact, their academic success rates are higher than whites. And without affirmative action.
You just ignored the entirety of the video that proves that you are wrong about the founding of the country. The founding fathers wanted immigration exclusively from Western Europe, not from fucking Somalia or Mexico.
1,000,000 isn't even a quarter of today's East Asian population in America, and Kennedy's immigration policy didn't really favor East Asia anyway.
In 1960, not only was this country overwhelmingly white compared to today, but also MUCH younger in its whiteness.
White people on average were about my age in 1960, as opposed to almost 50. That is radically different just from a cultural perspective.