Fifty years ago, in the midst of a fierce political debate surrounding the United States' immigration policies, a young senator named John F. Kennedy penned an essay called "A Nation of Immigrants." It was a groundbreaking book, asserting urgently and poignantly that our nation's greatness owes much to the immigrants among us.

As current headlines make clear, Kennedy's plea is as timely and necessary as ever. The United States is -- and always has been -- a nation of immigrants, though we continue to struggle to come to terms with the fact. Whether we're debating the merits of building a 1,952-mile fence to keep "them" out or arguing the constitutionality of legally enforced racial profiling, the immigration debate shows no signs of abating. Though there is no lack of emotionally charged rhetoric on all sides of the debate, seldom do we stop to consider who these immigrants actually are, and why they have left their families and risked their lives in a desperate attempt to find menial jobs that pay paltry wages.

During the making my new documentary, Return to El Salvador, I met Salvadorans who fled their homeland in the 1980s during the country's civil war. Eighteen months ago I couldn't have pointed to El Salvador on a map, but the more I learned about their story, the more disturbed I became. I discovered that their story was in many ways my story. I learned of the horrific ways in which United States policy had contributed to atrocities in this tiny Central American nation, and that these very policies were forcing hard-working, law-abiding people to flee for their lives.

It's a bitter irony: U.S. actions in El Salvador and elsewhere force migration north, and once here, policies are in place to ensure that immigrants' lives will continue to be exceedingly difficult.

Most recently, Arizona passed immigration legislation that even Tom Tancredo, one of the nation's most outspoken opponents of illegal immigration, has questioned. The bill, which requires Arizona police officers to question anyone they suspect of being undocumented, nonetheless maintains strong support in certain quarters. As irony would again have it, however, most of these supporters are themselves descendants of immigrants. Sarah Palin, for one, counts among her ancestors many who sailed on the Mayflower in search of a...