Current immigration and migration: Not to deny any of the real advantages to USA that have proceeded from immigration, but currently there is more to it:
The area where I live is over-whelmed by immigrants from the upper Midwest and Florida who like nothing about our local culture and want to change everything. I went to a home-schooling conference held last summer. The organization sponsoring it was local but of people from the areas I named. The M.C. had lived here for 17 years. Her accent was such as to suggest that she had not in all that time mingled with any local people but only with her own. The speakers she brought in were from Florida, which is hundreds of miles away. This is just a "for example." I could complain all day. I am experiencing culture shock in my own native community.
Immigrants from outside USA borders are presently coming in numbers too big to assimilate to and adopt the cultural beliefs and traditions that Americans have established with two wars (Independence and Civil), with our Constitution and other documents of freedom (Bill of Rights, Dec. of Independence, Magna Carta), with our religious influences. Immigrants in large numbers may change America faster and more drastically than it can beneficially absorb. Immigrants from places where all moral fiber had been destroyed by totalitarianism [former Communist Russia, former Yugoslavia (maybe parts of Mexico judging by crime statistics, though many Mexicans are more traditionally conservative and religious than the average contemporary American)], are worse than different; they are in opposition to civilization.
I hope krishna-agrawala's Post 5 vision for immigration laws can be realized. His was a good post.
Immigration does contribute to an America that is better. One of the essences of America is that it is the land of second chances. It is the refuge of those who have been ostracized and alienated from their indigenous cultural order. The Pilgrims were silenced voices, and they emigrated. The Europeans who came over were also individuals in search of a better life, primarily because the lives they were leading were ones that could have stood improvement. America has been the collection point for all of these individuals. In this respect, the absence of a strictly codified hierarchical order has been the attractive element to these individuals. In the modern setting, we still see this as immigration is something that has increased with ferocity and intensity. The faces may have changed, but the fundamentals behind their emigration is much the same.
I disagree slightly with the above answer. I believe immigration does contribute to a better America even when it is without legal permission.
It's a cliche, but we are an immigrant nation. Some of the best and brightest ever to grace the Earth have moved here for our freedoms and opportunities, not the least of which were Albert Einstein, Madeleine Albright, John Muir, Subranhmanyan Chandrasekhar and Martina Navratilova. But even the most ordinary immigrants come here with a dream and a work ethic, work much harder at the jobs no one else will take, put food in my grocery stores at low prices, pay taxes into my government coffers, and contribute a rich and vibrant culture to mix in with my own.
Even those here illegally prop up Social Security and Medicare with the taxes they pay, even though they'll never see a dime of it. They give me a virtual tax cut every time I buy a head of lettuce or some strawberries, since the prices are lower.
I can't imagine this country without immigrants.
Immigration does contribute and has contributed to making a better America. Now, it is not clear that illegal immigration in the amount that we seem to have now will also contribute.
Historically, immigration has been a good way to get new, ambitious, eager people to be part of the United States. The people who are willing to go to the effort of immigrating (and are brave enough to leave their home countries and the lives they know) are likely to be more ambitious than the regular run of people.
So, by allowing immigration, we have allowed many people who are highly motivated to come to America and help improve our country.
Most certainly, well designed and properly implemented immigration laws will contribute to development of a better America in Future by encouraging right number and right types of people into America according to the changing needs of its economy.
America or any other country for that matter does not have at all the times the right mix of people that it needs for meeting the current needs of its society as well as to contribute to its development needs. Take for example, if USA finds that it is short of trained and talented mathematicians for manning its laboratories that help the country to maintain its technological edge, then it cannot afford to wait for many years to train the existing citizen to take up such positions. The alternative of getting trained people from other countries is not only quick, in this ways the America saves the the money it would have spent on the upbringing and training of such person within America. Remember manpower is the most precious resource of any organization or society. And reliance of migrated work force enables America use this very valuable resource without paying a cent for its development.
The immigration laws will also help to reduce the problems of assimilation of new immigrants to adjust to and adopt the existing ways and culture of the country.