American society has often been described as a melting pot but in recent years, it has also attracted other definitions such as "tomato soup" and "tossed salad".
The Statue of Liberty has welcomed immigrants to the US since 1886
For centuries, the US has attracted people in search of a share of "the American dream" from all corners of the world.
In fact, US history is one of immigration.
In 1620, about 100 English colonists, so-called "Mayflower Pilgrims" left for America seeking religious freedom.
They landed near Plymouth, Massachusetts, marking an early successful European migration to North America, which had been inhabited by Amerindian people for more than 16,000 years.
The immigration flow to the US first accelerated after the French Revolution, and during the 19th century, population pressure, fragmentation of land in rural Europe and famines drove millions of Europeans to the New World.
Throughout the 19th and 20th Centuries, American ports teemed with German, Chinese, Irish, Italian, and Polish immigrants.
Until 1882, the US government practised an open door immigration policy, but at the end of the century, it began trying to control immigration by excluding prostitutes, criminals, alcoholics, and Chinese, among others, from coming to the country.
During the 20th Century, the US government kept fine-tuning its immigration policies.
Some 16m people passed through Ellis Island from 1892 to 1924
Under the national origins quota system, established in 1921, admission to the US largely depended upon an immigrant's country of birth.
Seventy percent of all immigrant slots were allotted to citizens of just three countries: UK, Ireland and Germany.
But these went mostly unused, while there were long waiting lists for the small number of visas available to those born in eastern and southern Europe.
In 1965, the nationality quotas were abolished, which is seen to have inaugurated a new era of mass immigration, particularly from Mexico and Latin America.
In an effort to curb illegal immigration, in 1996 Congress passed legislation which marked a turn towards tougher policies for both legal and illegal immigrants.
It increased the categories of criminal activity for which immigrants, including green card holders, could be deported, and imposed mandatory detention.
As a result, more than one million individuals have been deported since 1996.
While critics of illegal immigration are pushing for even tougher laws, mass demonstrations across the US have shown that such a strategy will not be accepted by a large section of the population.
The immigrants' campaign groups argue that a country built by immigrants will fail to function without them.
Americans take pride in their "melting pot" society (a term coined by an immigrant, Israel Zangwill) that encourages newcomers to assimilate into the American culture.
But the melting pot imagery has been contested by the idea of multiculturalism, the "salad bowl theory", or as it is known in Canada, the "cultural mosaic", whereby the immigrants retain their own national characteristics while integrating into a new society.
Some go further. Harvard political scientist Samuel Huntington says that large-scale Latino immigration poses a threat to American identity.
According to Professor Huntington the reality of American history is best described as tomato soup: the blending of new ingredients adds spice without compromising the essential character of tomato.
"Contributions from immigrant cultures modified and enriched Anglo-Protestant culture of founding settlers.
"The essentials of that founding culture remained the bedrock of the US identity, however, at least until the last decades of the 20th Century," Mr Huntington writes in his controversial 2004 book Who Are We. The Challenges to America's National Identity.
He sees the gravest threat to American identity in Mexican immigration which, according to him, is splitting America in two.
"As their numbers increase, Mexican Americans feel increasingly comfortable with their own culture and often contemptuous of American culture", he says.
Sense of history
But are the Mexican-dominant areas of the US really consolidating themselves into a culturally and linguistically distinct and economically self-reliant bloc within the US, as Professor Huntington states?
Douglas Rivelin from the National Immigration Forum contests Mr Huntington's view of Latinos as different from other immigrant groups.
"I was astounded that someone so smart could write such a book," he says.
"He is totally missing what is going on in the US. The same thing could have been written in 1924 about Irish or other immigrants, and it would have been equally wrong."
"Bagels and pizzas and spaghetti were new things at one time... immigrants come and change America and are changed by America."