After 12 years of endless war; after Afghanistan, after Iraq, after Libya, after the drones in Pakistan, Yemen and Somalia, the American people have had enough. There is perhaps no better explanation for the rather remarkable situation unfolding right now in Washington. President Obama has gone to the US Congress to ask for a military authorisation for the use of force against Syria after its international-norm-breaking use of chemical weapons against its own people.

Such requests are something of a pro forma exercise for US presidents. When the commander-in-chief wants to go to war, Congress is usually happy to comply (if it is even asked for permission, which is rare). This time, Congress is refusing to bite. Whip counts in the US House of Representatives indicate overwhelming opposition and not just among the president's political opponents in the Republican party but also among Democrats. Public opinion polls show that a majority of Americans are strongly against US involvement in Syria.

What is perhaps most surprising about this is that the Obama administration is seeking authorisation for a rather limited use of force. It is loudly proclaiming that there will be no US boots on the ground, no effort at regime change, no direct engagement in the Syrian civil war – just a few cruise missiles to uphold a global norm and teach Bashar al-Assad a lesson. Yet, while Obama will speak to the American people and make his case for military intervention on Tuesday, few political observers believe he will win the day (though one cannot fully discount the possibility).

It is an extraordinary turn of events and one that goes so strongly against the currents of recent history that it may come to represent a sea change, not just in how the US employs military force in the future but in the very construct of American foreign policy. No longer, it appears are Americans and Congress willing to give the commander-in-chief a virtual blank cheque.

So why is this happening?

Part of the reason is undoubtedly politics. Republicans, who in recent years have rarely met a military engagement they didn't enthusiastically support, would sooner cut off their right arms then give Obama anything that he actually wants. Yet their opposition to involvement in Syria also reflects a growing division within Republicans, between the party's neoconservative national security elite and its long-dormant isolationist wing. Indeed, the congressional vote on Syria may preview a titanic struggle over the foreign policy direction of the Republican party.

As for Democrats, particularly liberals who opposed the Iraq war and were ambivalent about the Afghanistan surge, even party loyalty may not be enough to get them to go along with the White House's plans. Unlike Obama, members of Congress will be on the ballot in 2014 and few of them are going to want to stick their neck out for a military strike that has little public support.

Beyond the political gamesmanship, opposition is due in large measure to the fuzziness of the White House's strategic plan. While norm enforcement and deterring future chemical attacks can be a justifiable rationale, the idea that the US would engage Syria over one category of weapons while doing nothing to stop the civil war that has taken 100,000 lives seems to many to be illogical. Moreover, the lack of clear strategic objectives, or a vital US national interest or even a fallback plan if Assad is not deterred from continuing to gas his people, is raising real doubts about the efficacy of intervention. And truth be told: the White House has done a dreadful job of making the case for war.

In August 2012, Obama laid down his infamous red line about the use of chemical weapons on Syria. Everyone assumed this meant that the US would engage militarily. But in the year since, he has made virtually no effort to prepare the public for that possibility. There was, from all appearances, little private consultation with Congress lining up support for a possible response and the administration position on Syria has long oozed with indifference about US involvement.

But when videos appeared showing hundreds of Syrians lying dead from an apparent chemical attack, the administration grabbed the biggest hammer in the toolbox and immediately started talking about launching cruise missiles and dropping bombs on Damascus. They completely misread the public's appetite for yet another war and were further blindsided by David Cameron's stunning failure to properly manage a parliamentary vote authorising British involvement in a military strike.

Obama's decision to go to Congress for authorisation reflected belated recognition of the emerging political reality and, at the time, looked like an inspired political move. But confidence that Congress would obediently go along with the president's plan (if one wants to be generous and call it that) was misplaced. Faced with growing congressional opposition, the administration is now taking the low road of fearmongering that a failure to punish Assad will embolden Iran, put Israel in danger or perhaps allow chemical weapons to fall into the hands of terrorists.

The White House finds itself in a political no-man's-land. Winning a vote in Congress will mean squandering political capital and twisting Democratic arms – all in pursuit of a military strategy that will, by the White House's own admission, do little to stop the bloodletting in Syria. Lose the vote and risk becoming a weakened lame duck three years before Obama's second term is up. Of course, Obama could ignore Congress, but then he risks entering into impeachment territory.

Yet, for all the short-term political fallout, the apparent train wreck on Syria might be the best thing to happen in American politics in a long time.

Since 11 September 2001, armchair generals (inside and outside government) have planned one military engagement after another and confidently predicted success – and then dodged accountability after repeated failures. The result has been quagmire after quagmire, trillions of dollars in costs and tens of thousands of dead and maimed Americans.

Those chickens have come home to roost. No matter how defensible the plan for military action in Syria might be; no matter how strong the impulse to punish the use of long-banned weapons; no matter how many assertions of limited engagement are made, Americans and their representatives in Congress appear finally resistant to buying the war-makers' tonic (some might say 10 years too late).

The desire of America's foreign policy elite to continue to demand that the US remain the indispensable nation and the world's policeman has come face to face with a public tired of war and tired of foreign policy failure. And the American people look poised to win this round.

This article originally appeared on guardian.co.uk