This is a very sensitive issue because people get very passionate talking about this subject. I was born in Los Angeles, CA, USA. My parents are both from Mexico and of course I am very proud of my Mexican heritage.
I think that European Americans (whites) are frightened because they see themselves becoming less and less of the majority here in the US. Latinos (Hispanics), or people of Latin American backgrounds, (Mexicans, Puerto Ricans, Cubans, Salvadorans, Guatemalans, Hondurans, Nicaraguans, Ecuadorians, Colombians, Peruvians, etc.) are now the second largest ethnic group in the US. Latinos have overtaken African Americans (blacks) and are largest minority group in the US.
In the state of California, Latinos account for about 30 % of the population. Latinos have a high birth rate and can quickly increase their numbers in the near future. So I feel that Whites seem frightened because they want to retain control politically and economically from all the other groups that live in the US.
A Little History
The southwestern section of the United States has a large influence of spanish speaking people since the Spanish claimed it during the early 1500's. The problem of illegal immigration to this part of the US has always been an issue since the United States fought and took California, Arizona, Nevada, Utah, 3/4 of Colorado, New Mexico, Texas, 1/4 of Kansas, parts of Wyoming and Oklahoma in 1848 from the Republic of Mexico. That being said the Spanish/Mexican culture along with its people have existed in these parts of the US for at least 500 years. Many of the people that come this country from Mexico and other Latin countries come to work and to pursue a better life for themselves and more importantly their children.
Now let's look at the Europeans. Many came to escape religious persecution, oppression from a number of European countries during the 1500's, 1600's, 1700's, 1800's, and 1900's. The Native Americans, which people by mistake call Indians, are the original peoples of North and South America. The Europeans came and just simply took control of their land and disrupted their lives. There is further evidence of this in other parts of the world. Just look at South Africa, Australia, New Zealand, Zimbabwe and other places where the Europeans came and told the native people to leave.
Now some people of the US are acting by being against illegal immigration but they should remember that their ancestors came from a far away continent and established their lives here. Now in my opinion this was also illegal immigration of grand proportions because their ancestors almost wiped out an entire race of peoples and cultures and established theirs.