Definitely good data you have. I definitely agree with this change. Its not even exclusive to USA. Many European countries had huge population moves from around the world.
I also wanna add to this honestly, I am pretty sure young generations are less xenophobic and more liberal. They are nearly always pro-minority. White nationalism is seen as something very eccentric and poisonous. These obviously influence voting. USA had low turnout rate in past but now these new "gen z" likes politics. This is actually positive for USA in my opinion.
Actually this is something that is unique to the United States. I don't think that any of the European countries have undergone transformation of this magnitude. Among all the European nations, Sweden may be the country with the largest share of migrants. Even there, the migrants and their descendants comprise only around 20% of the population. In case of the United States, recent migrants (post-1945) and their descendants comprise almost half of the population. And I am not sure whether this has led to a decrease in xenophobia, because I am reading about a lot of racist incidents nowadays.
Now coming back to the topic, the failure from the part of GOP is that they have failed to attract the recent immigrants (except the white immigrants). Among Asian, African and Hispanic immigrants, the GOP trails the Dems by at least 40-45 points. There have always been sections of non-whites in the US who have supported the GOP. Examples are Vietnamese migrants who opposed Viet Kong, evangelist Hispanics and Cubans. But Republicans have failed to expand their support base apart from these core groups.