By definition, the U.S. policy on immigration is codified in the laws passed by Congress. The current situation is largely the product of the Immigration and Naturalization Act of 1965, Now...
"By the end of the 20th century, the policies put into effect by the Immigration Act of 1965 had greatly changed the face of the American population. Whereas in the 1950s, more than half of all immigrants were Europeans and just 6 percent were Asians, by the 1990s only 16 percent were Europeans and 31 percent were of Asian descent, while the percentages of Latino and African immigrants had also jumped significantly. Between 1965 and 2000, the highest number of immigrants (4.3 million) to the U.S. came from
Mexico, in addition to some 1.4 million from the Philippines. Korea, the Dominican Republic, India, Cuba and Vietnam were also leading sources of immigrants, each sending between 700,000 and 800,000 over this period."
We also currently have over ten million "illegals," mainly from Mexico, as well as a couple million "anchor babies" born in the U.S. to the illegals, who are legal citizens due to a disastrous misreading of the Fourteenth Amendment by the United States Supreme Court. Thus, it is only a question of time before essentially all of the families of these anchor babies are granted U.S. citizenship.
In short, we are fucked.