Okay, let's look at an example. Mexicans are not "alien" to California, Texas, New Mexico or even Arizona. The've been here since before these states were admitted to the Union and have maintained a lot of their unique traditions. This makes the culture of these states different than those of the South or the Midwest or any other part of the country.
Personally, I'd feel downright uncomfortable in the South for a LOT of reasons.
Firstly, the Criollo Hispanic culture that remained in areas in the Southwest was very different from the culture that is coming from the most recent immigrants to these areas. The Criollo Hispanic people, whose ancestors have been in these lands for hundreds of years, have a far more European influenced culture and their traditions reflect that. Also historically, they have been far less likely to embrace radical ideas such as equality and democracy.
I was also state that the overall influence they had on the region was very minimal compared to the Anglo-Celtic people and culture.
So, it's about "white culture."
Here's the interesting thing about the United States. Our culture is extremely flexible. The Founders wouldn't recognize very much of it, partly because of technology but also partly because people have been coming here since the colonial days and bringing the spice of their culture. Personally, I love it. It makes life interesting.
Well not necessarily white culture, but civilized culture that comes from Europe and specifically the British Isles. Many Canadians have this shared heritage and the similarities between the traditional population of America and the traditional population of Canadians reflect this.
Also, I would be concerned if ANY large ethnic group were to replace the traditional American population. Some of my ancestors were part of the waves of immigrants I felt were hurtful for the overall national character. Also, culture is far more than just technology.
And like you, I am in love with experiencing other cultures, languages, traditions, and ways of life. I am especially a lover of food from other cultures.
I am however against any population of people in the modern world being displaced.