Leo Manzano is the son of an undocumented farmworker from Mexico. Meb Keflezighi and his family fled civil war in Eritrea. Danell Leyva's stepfather defected from Cuba's gymnastics team during a meet in Mexico and swam across the Rio Grande River to reach America.

More than 40 foreign-born athletes represented the United States in the London Olympics. (Manzano and Keflezighi are runners; Leyva, a gymnast.) And that total does not include the children of immigrants, including the entire women's table tennis team -- Ariel Hsing, Erica Wu and Lily Zhang -- who are all Chinese-Americans.

Their stories reinforce an enduring truth: Our lifeblood is constantly enriched by the infusion of new immigrants. We are a far better country because people come here from all over the world to improve their lives and follow their dreams. Some create high-tech companies like Google and Intel; others cut lawns or clean houses. And a few can hit a pingpong ball really hard.

As a country, we've always been ambivalent about immigrants. We tear up at the Statue of Liberty and fondly remember our own origins, and then resent the latest wave of newcomers as a threat to American culture and character. At one time, the Irish were barred from many jobs; Italians were considered nonwhite and subjected to racial bias; Jews were banned from clubs and universities. During World War II, 120,000 Japanese were interned as a security risk.

Today, our nativist impulse focuses on Latinos and Muslims. Consider Sheriff Joe Arpaio, conducting his own version of the Mexican-American War in Arizona, or five Republican congressmen, insanely accusing an aide to Secretary of State Hillary Clinton of fronting for the Muslim Brotherhood.

Those haters were always wrong. And our Olympic team vividly demonstrates how wrong they are today.

In the summer of 2000, Lopez Lomong was 15, a victim of Sudan's civil war living in a refugee camp in Kenya. He had never watched television before and had no idea what the Olympics were. But when he saw American sprinter Michael Johnson line up for the 400-meter run, he had this reaction: "All I knew was the camera focused primarily on one man, a man with skin the color of mine. Across his chest were three letters: USA. He was about to change my life."

That night, Lomong decided to become a runner and compete for the United States in the Olympics. A year later, he was rescued from the camp and placed with a foster family in upstate New York. In 2008 he made the Olympic team, losing in the semifinals of the 1,500-meter race in Beijing after his hamstring tightened. This year he ran 5,000 meters in London, and he recently described his feelings in The New York Times:

"Before coming to America at the age of 16, I felt lost, without a country. I never identified with any flag; instead I was an outcast from a country at war ... For me, competing in the Olympic Games has been an opportunity to thank a country that opened its arms to me 11 years ago, showing me that I mattered."

Athletes like Lomong make an impact far beyond their home countries, however. They reveal the huge benefits of globalization, the constant movement of people and capital, ideas and information, across national boundaries.

Volleyball player Foluke Akinradewo was born in Canada of Nigerian parents. Raised in Florida, she holds citizenship in three countries. Archer Khatuna Lorig is the first athlete to compete in the Olympics under three flags: the Soviet Union in 1992, her native Georgia in 1996 and 2000, and the United States in 2008 and 2012.

Distance runner Bernard Lagat grew up in Kenya and caught the eye of American scouts who helped him win a scholarship to Washington State University. There, according to Runner's World, he fell under the influence of James Li, "a mystical Chinese coach with revolutionary ideas how to turn a wide-eyed Kenyan into a world-class miler." After winning medals in two Olympics for Kenya, Lagat became a U.S. citizen, and London marks the second time he's represented his new country.

That makes him a native of Kapsabet, Kenya, who attended college in Pullman, Wash., under a Chinese coach. Today he lives in Tucson, Ariz., and spends summers training in Tubingen, Germany. His uniform says USA, and we're lucky to have him. But it could also say WORLD.

Steve and Cokie Roberts can be emailed at stevecokie@gmail.com