The United States, the country par excellence of the immigration fact, constitutes the most important area of immigration in the world today. Between 1820 and 1990 the "empty continent" has welcomed more than 55 million people from the most diverse places on the planet. American immigration presents very peculiar features, and offers clear differences with respect to that which takes place in Western Europe. These differences refer both to the volume of flows and their composition and to the social perception of the migratory phenomenon. American society has been born of immigration and has developed with the contribution and effort of immigrants. One of the essential components of North America's image of itself is its history as an immigrant nation. Immigration is a substantial part of its national mythology, unlike in Europe where the essence and origin of different nations has been justified in cultural homogeneity. In societies that were considered perfectly configured, like the French, the contribution of immigrants has never been valued as a contribution to the creation of their people, which since the Revolution of 1789 was already presented as a finished whole. On the contrary, it has been seen as a temporary aid or relief for its development, and as a long-term problem against national and cultural unity. Although almost all Americans are or are descended from immigrants of greater or less seniority, or precisely because of this, American history has lived permanently immersed in an endless debate on immigration: what immigrants to admit, how many, with what characteristics ... and around the balances in the mix of ethnic and cultural origins .
This debate has been revived at times of increased migration and, above all, transformation of its composition, and it shows the collision between the pressures of recently arrived immigrants, the interest of ethnic-cultural groups of origin older - who see their relative weight decrease in society - and the demands of the labor market. The discussion about assimilation, integration or pluriculturalism is particularly intense within the American society. The xenophobic reactions of "nativists" against immigrants have been argued in the impossibility of their Americanization, and in the risk that this would entail for American society. They intensified from the eighties of the nineteenth century, when the change in the origin of the newcomers began and a strong and uninterrupted rise in the number of immigrants, which culminated around 1910. It was then attended a displacement in the traditional wave of European immigration coming from the countries of the North and the West (Great Britain, Ireland and Germany, fundamentally) to those of the East and the South of Europe, at the same time as the influx of Asians intensifies. Especially Chinese who fled the poverty of the Canton region and were recruited in the United States by the demand for labor that produced the "gold rush" in California and for the construction of railroads. The "nativists" expressed a clear hostility toward non-English speaking immigrants. The aversion was particularly directed towards the Asians, until culminating in California with the promulgation of the "Chinese Exclusion Act" in 1882.
