There's a seasonal change going on in the country, and I'm not talking about the way the early snows are lingering in the uplands woods and ridges. It's happening throughout the country, it's affecting how America looks at itself and at the world, and before long, it will almost certainly affect how America behaves in the world.

There have been whispers of change in the wind, the natural force that Robert Frost, in a poem called "Clear and Colder," called the "season-climate mixer." One of them was the way the nation marked the 2,000th death in Iraq this autumn; no such ceremonies of sadness marked the passage of that boundary during the Vietnam or Korean wars. One of them was the way Congress is beginning to show signs of impatience with the open-ended nature of the commitment to Iraq; there is more national impatience now than there was at a similar period of the Vietnam conflict. And one of them was the startling demand by Pennsylvania Rep. John P. Murtha Jr. -- a decorated Marine (a Bronze Star and two Purple Hearts) who fought in both Korea and Vietnam (and who is a retired Marine reserve colonel) -- that the United States start withdrawing troops from Iraq.

It turns out that these are not random occurrences in a season of contention, but something more than that. Americans are growing more skeptical of involvement abroad. (Historically that's more of a Republican impulse than a Democratic one, by the way.) And though it's hard to resist the temptation to say that the Iraq war is the reason, it's best to remember that Americans, who were late to join both world wars, have never relished the world stage. We have always found plenty to fight about at home.

Indeed, poll data shows that 42 percent of Americans believe that the United States should "mind its own business" internationally -- statistically pretty much identical to the 41 percent who said the very same thing in 1976. Lest you think that comparing American views a year after Saigon fell and nearly three years into a controversial war is manipulating the number, please note that the percentage of Americans who felt that way in 1995 -- when nothing much was going on internationally and the United States was sitting proud and pretty atop a one-superpower world -- was 41 percent.

This and other data in a hefty report from the Pew Research Center for the People and the Press and the Council on Foreign Relations paint a picture of a nation weary of the world's worries -- a feature of contemporary American culture that will surely shape next year's midterm congressional elections and the presidential elections that follow two years later. President Bush may have run as a wartime president two years ago, but the terms of engagement in 2008 will almost certainly be different and, if the war is still going on, even more acrimonious.

Polls rarely tell us anything interesting, and even more rarely do they tell us something significant, but this time the surveys tell us something that is both interesting and significant. They say that most opinion leaders believe the United States will not establish a stable democracy in Iraq -- but that a majority of the public thinks the American mission in Iraq will prevail.

No such polling was undertaken during the Vietnam years, but it was clear that in the early days of the conflict in Southeast Asia, prominent Americans believed deeply in the U.S. effort. Faulty memories and folklore have warped the way many Americans understand and remember the Vietnam period, but it is important to note that the debate in those years wasn't over whether the war was worthwhile or moral; almost everybody agreed that it was. Instead the dissent came from those, including prominent members of the establishment press, who believed the United States was failing in a noble cause. David Halberstam, the young New York Times reporter who so angered President Kennedy, didn't believe the American role in Vietnam was immoral. He believed the way the American role was being played out in Vietnam was incompetent.

This is a different situation entirely -- one of many, as I have argued repeatedly, that shatter the (frequent and facile) comparisons between Vietnam and Iraq.

What is not different, though, is that an American war in a land far away -- against an opponent hardly anyone at West Point or Annapolis or Colorado Springs was trained to fight -- is dividing Americans. The pre-Thanksgiving plea for peace from a man of war like Mr. Murtha only heightened the level of contention.

An Ohio congresswoman raised questions about Mr. Murtha's courage, setting off a furor that, like the time Thomas Hart Benton of Missouri called Henry Foote of Mississippi a coward during the Senate debate over the Compromise of 1850, nearly brought grown men to blows. The word "pathetic" was hurled around the chamber. Liberals who regarded Mr. Murtha as a recondite apologist for military interests embraced their new ally as an eminent sage. Within hours, conservatives were deriding Mr. Murtha as a Keystone version of Howard Dean. It took President Bush himself, speaking in Beijing, to cool the dispute. He pronounced Mr. Murtha "a fine man, a good man," though clearly, in the president's view, a misguided man.

The uproar on Capitol Hill did what Washington contretemps so seldom do in an age of Astroturf grass-roots: reflect the public back home. Americans have strong feelings about this war and their role in the world, and those strong feelings have led to frustration. Even the people who say they absolutely, positively know what to do aren't absolutely, positively sure of the implications of those views. They may have their doubts, but do not doubt for a minute that this is a moment of transition for America in the world. Americans may not be withdrawing from Iraq, but slowly they are stepping back from center stage on the globe.

Commentary:
David M. Shribman is executive editor of the Post-Gazette (dshribman@post-gazette.com).