Sobered by the chaos that has ensued in Iraq since the fall of Saddam Hussein’s regime, the United States appears to be making a course correction. The Bush administration is expediting plans to return power to Iraqis and, instead of ignoring the United Nations, asking it to lend a helping hand. Rather than confronting “rogue nations” with the prospect of regime change through force, Washington has been sitting at the negotiating table with Libya, Iran and North Korea.

These are welcome developments – both for Americans who have bemoaned the erosion of a centrist brand of U.S. internationalism and for people around the world who have come to resent Washington’s overbearing ways.

It is too soon, however, to presume that the United States is rediscovering the path of moderation. The new tack represents a tactical response to the troubles in Iraq, not a deeper strategic shift. Furthermore, secular changes in American politics, not just the idiosyncrasies of George W. Bush and his neoconservative advisers, are pushing the country away from liberal internationalism. Even if the Democrats win the presidency this November, a more diffident and difficult America may well be here to stay.

America’s embrace of liberal internationalism began in the 1940s, when President Franklin Roosevelt used the backdrop of World War II to build a bipartisan coalition behind multilateralism. The strategic imperatives of the Cold War sustained this centrist coalition for the next five decades, but it unraveled soon after the Soviet Union’s collapse. By the second half of the 1990s, President Bill Clinton, although an avowed multilateralist, found his hands tied by domestic politics, with Washington keeping its distance from the Treaty to Ban Landmines, the International Criminal Court, and the Comprehensive Test Ban Treaty.

The election of George W. Bush dramatically accelerated these go-it-alone tendencies. Bereft of its internationalist wing – Bush p?re, Henry Kissinger, and Brent Scowcroft wield influence, but no longer power – the Republican Party has veered toward a hard-charging unilateralism shaped by the ideological convictions of the neoconservatives in Washington and the populist preferences of the party base in the heartland. The terror attacks of Sept. 11, far from pushing the administration back toward a centrist internationalism, bred an angry vulnerability that put extremist voices in command. The moderates, Colin Powell most prominent among them, have been embattled ever since.

To be sure, the proclivities of the Bush White House are in important respects unique. Should the influence of neoconservatives weaken or the Democrats take back the White House, the current penchant for unfettered and unflinching primacy would abate.

Nonetheless, it would be illusory to presume that a change of personnel or party will bring back America’s liberal brand of internationalism. A weakening of internationalist leadership is taking place across the political spectrum, not just among Republicans. Retiring from politics is the generation of Americans that fought in World War II and oversaw the building of the West. These seasoned leaders are being replaced by a younger generation that lacks the experiences and memories that have long served as the foundation of liberal internationalism. Moreover, the threat of terror is here to stay and will continue to advantage the extremes, not the moderate center.

So too is populist politics – and its aversion to submitting America’s will to the preferences of others – animating Democrats as well as Republicans. Demographic shifts are strengthening the political power of the South and interior West (the home of heartland populism) at the expense of the Northeast (the home of the liberal establishment). It is no accident that the Democratic candidates for president have been reaching out to voters who drive pick-up trucks.

Finally, the increasing polarization of U.S. politics does not augur well for the restoration of liberal internationalism. The right is moving to the right and the left to the left, with common ground increasingly scarce. Moreover, the divide is falling along geographic lines; the coasts tend to be liberal and Democratic, the heartland conservative and Republican. An ethnic dimension complicates the picture further, with a swelling Hispanic population growing more powerful in important electoral states like California, Texas and Florida – a main reason President Bush recently irked some of his staunchest supporters by embracing an immigration policy popular among Latino voters.

The intensity of political and sectional divisions will hinder the formation of an internationalist consensus that cuts across party and region – just as such divisions did earlier in U.S. history. Roosevelt succeeded in repairing these divides only by forging a coalition of moderate Democrats and Republicans and building an unprecedented alliance between North and South. With today’s Democrats and Republicans engaged in trench warfare and the coasts and heartland diverging politically as well as culturally, the restoration of a bipartisan center appears to be a remote prospect.

The worst of America’s excess on the global stage may be behind us. But the task of bringing the United States back to a liberal brand of internationalism is just beginning.

Charles A. Kupchan, a professor of international affairs at Georgetown University and a senior fellow at the Council on Foreign Relations, is the author of “The End of the American Era.” He will discuss U.S. relations with Europe at the Camden Conference, Saturday, Feb. 28 in the Camden Opera House. This commentary was originally published in The Financial Times.