Why do some people hate immigration?

Today, the United States has become the most powerful country and the most developed country in the world, with GDP reaching 19 trillion US dollars and per capita GDP exceeding 50,000 US dollars. It is the target of immigrants from many countries. Immigrating to the United States represents a high welfare and high quality life. Mexico has a relatively backward economy and a large population, with a per capita GDP of less than $9,000, but a population of 65.438+0.3 billion. Moreover, Mexico is full of violent crimes, drugs are rampant, the government's control ability is poor, and public security is naturally poor. So Mexicans want to be Americans every day, and people from American countries except Canada want to immigrate to the United States. Every year, there are hundreds of thousands of people who sneak into Mexico and other American countries from the US-Mexico border, just like crucian carp.

So, how can the United States let Mexico join the United States Federation? Americans can't enter the position of world hegemony through hard work. How can they share the world hegemony dividend with more than 654.38 billion Mexicans? Even Mexicans themselves complain about the Mexican government. Mexico was defeated, why was it not completely annexed by the United States? If the United States annexed Mexico, Mexicans would not have to sneak into the United States, and they would automatically become Americans. In fact, Mexicans think too much. The United States only wants Mexican land, not Mexicans. For the United States, more than 654.38 billion Mexicans are a burden, and the territory of the United States has long been enough.