"The impact of immigration — legal and illegal — on jobs, schools, healthcare, the environment, national security, are all very serious problems," insists Rep. Tom Tancredo, R-Colo., a man famed for his extreme anti-immigration views. "But more serious than all of them put together is this threat to the culture. I believe we are in a clash of civilizations." Tancredo's right about that last bit. We are in a clash of civilizations — and someday, immigrant culture might even displace some aspects of American culture.

We'd better hope so.

Americans? We're fat, decadent and getting dumber all the time. Our life expectancy, which rose for most of the last two centuries, is stalling because so many of us are obese. While most of us know everything there is to know about Paris Hilton, we know next to nothing about history, geography, international politics or the workings of our own government.

In American culture, the Xbox reigns supreme among boys, we market thong underwear to prepubescent girls and a growing number of adults think a McMansion with fewer than one bathroom per resident is the height of privation.

Our forebears tamed the West, but today, most of us couldn't tame a paper bag. If we had to cross the country in covered wagons, we'd be dead well before we reached the Mississippi.

Now contrast "our" culture with that of recent immigrants. On all too many measures, immigrants look a whole lot better.

Immigrants exhibit no shortage of pluck. It takes guts to leave your home and everything you know — even if a green card awaits. And when it comes to illegal immigrants, just getting here takes astounding courage. Illegal immigrants endure astonishing privation and risk — just for the chance to improve their lot by doing the backbreaking work so few native-born Americans have the inclination to do. While we demand McMansions, they share cramped apartments. We're up to our ears in consumer debt; they save almost every dollar to send to their less-well-off relatives.

The younger generation of illegal immigrants is particularly impressive. Each year, thousands of unaccompanied children cross into the U.S. without their parents, many literally walking here from villages in El Salvador and Guatemala. Could our sheltered and chaperoned children manage such a trip on their own?

Immigrants tend to be straight arrows too. A 2002 survey by the nonpartisan group Public Agenda found that an overwhelming majority of immigrants believe that they have a duty to "work hard and stay off welfare" and "respect people from different religious and ethnic backgrounds." A Harvard study found that immigrant students also have more positive attitudes toward education than U.S.-born young people.

And contrary to widespread perceptions, immigrants are less likely than nonimmigrants to commit crimes. A study in Chicago looking specifically at Mexican immigrants found that "first-generation immigrants (those born outside the United States) . . . were 45 percent less likely to commit violence than were third-generation Americans." Harvard sociology professor Robert Sampson suggests that increased immigration may have been a factor in reduced crime rates in the 1990s.

Another study done in New York City found that immigrants looked pretty good across the board. Compared to their native-born peers, for instance, "foreign-born (adolescents) had less asthma, less obesity, fewer school days missed and less involvement in substance use, sex, delinquency and violence." On average, immigrants even live three years longer than the rest of us.

No wonder Tancredo and his supporters are terrified of immigrants!

Immigrants put us to shame. They're healthier, stronger, thriftier and braver. If we can't get them to assimilate, they may well displace us. Thursday's death-by-filibuster of the immigration reform bill — which ended the prospect of a path to citizenship for 12 million undocumented workers — might slow the cultural displacement, but it won't stop it.

Fortunately for us native-born types, most immigrants are willing to overlook our flaws and assimilate. According to the Public Agenda survey, 80 percent of immigrants consider the U.S. "a unique country that stands for something special in the world," and 87 percent say it's "extremely important" to "speak and understand English."

But we should pause before we insist that immigrants assimilate. The same studies that show immigrants are healthier and less violent also suggest that the inoculating effects of immigrant status wear off over the years. By the time you get to the grandchildren of immigrants, you can no longer detect much difference.

In other words: Immigrants beware! Assimilation into American culture may be hazardous to your health and your values.

As for the rest of us — instead of insisting that immigrants assimilate to our culture, maybe we should consider assimilating to theirs. It might be the only way to bring back the values of our ancestors — who were, as everyone knows, immigrants themselves.

Rosa Brooks is a professor at the Georgetown University Law Center. She wrote this commentary for the Los Angeles Times. Reach her at rbrooks@latimescolumnists.com