Nowhere will this have more of an impact than in the broader Middle East, where the president has placed his most substantial wagers.
Obama's domestic victory polarises US foreign policy
Senator John McCain declared on Monday that the passage of President Barack Obama's health care legislation had angered Americans from the heartland. "We are going to have a very spirited campaign coming up between now and November. And there will be a very heavy price to pay for it," the Arizona Republican and former presidential candidate warned. Mr McCain was speaking about domestic electoral politics. However, in the divisive atmosphere following the Democrats' approval of the health bill in the House of Representatives, over unanimous Republican opposition, it would be naive to assume that the rancour will be contained there. During his campaign, Mr Obama portrayed himself as a man of consensus. One might debate the merits or faults of his health plan, but his legislative victory has only confirmed him as one of the most polarising presidents in recent American memory.
Polarisation is not necessarily bad. Many of America's great legislative initiatives, from the New Deal to the civil rights acts, provoked lasting resentment in sections of American society, because they so profoundly changed the nature of the country's political and social order. Mr Obama's willingness to go all the way on health care may well define his legacy. But it will also hinder him when it comes to foreign affairs, and nowhere will this have more of an impact than in the broader Middle East, where the president has placed his most substantial wagers.
That doesn't mean that Republicans, out of sheer spite, will oppose each and every regional initiative of the president. If there is one place where agreement has survived between the two parties, it is foreign policy, and that is especially true in the Middle East. Mr Obama's accelerated withdrawal timetable from Iraq is popular; his positions on the Palestinian-Israeli conflict have not lost him core support; his favoured approach for addressing Iran's nuclear programme, with its mix of dialogue and sanctions, is acceptable to most voters; and even judgment of the president's surge in Afghanistan is on hold until July 2011, when American forces are scheduled to begin withdrawing.
Yet Mr Obama will also find his margin to manoeuvre severely constrained on all of these issues in the coming year, now that he has incurred Republican wrath and taken on an enormous financial burden through his health plan. In fact it's hard to see how he can avoid this. Take Palestinian-Israeli peace negotiations. It was, perhaps, no surprise that Israel's prime minister, Benjamin Netanyahu, hardened his position on settlements while visiting Washington this week. Mr Netanyahu knows that with Congress in its current state, it will be very difficult for Mr Obama to pressure his right-wing government in the coming months. Neither Republicans nor Democrats have an incentive to pick a fight with Israel before congressional elections - Democrats, because they will need all the votes they can garner to retain their seats come November, given the unpopularity of the health care bill; Republicans, because defending Mr Netanyahu will be a way of thwarting the president.
And this goes beyond the power of a "pro-Israel lobby". In polarised environments, differing constituencies coalesce to pursue parochial agendas. Israel's backers, if they play their cards right, could rally, for example, conservative Christian groups (who regard Mr Obama as too liberal) or national security hawks (who believe the high cost of his health plan will make America weaker militarily) against the president's preferences. This could give Congress cold feet when it comes to granting Mr Obama the leverage he needs to negotiate peace.
The discord over the health plan will also limit the president's options in Iraq. Senior American officers in the country, even the former US ambassador in Baghdad, have advised that the United States retain flexibility by keeping more combat troops in the country beyond the September 1 withdrawal deadline. Given the post-election confusion in Iraq today, and the possibility of months of political wrangling, this seems wise. Yet Mr Obama is far less inclined to listen to such advice now that any delay might be turned against Democrats at election time.
The price tag of the health care bill will also curb the president's options with respect to Iran and Afghanistan. The Obama administration has always factored potential economic costs into its Iran strategy. A war, many people in Washington believe, would have ruinous consequences for the world economy. But if that assertion could still be debated before the health care bill, it no longer can be. With a price tag of $940 billion (Dh3.5 trillion) over the next 10 years, with many American states running crippling deficits, and with global finances still fragile after the 2008 crisis, Mr Obama will think longer and harder than ever before engaging in military action against Tehran, or allowing Israel to do so.
Much the same is true in Afghanistan. When he announced his Afghan plan, Mr Obama saw money as a major factor in making it sustainable. His promise that a pullout would start in the middle of next year was as much a financial calculation as a political one. The cost of health care may force the president to stick to his pledge in a more rigid way than he initially intended. Worse, if the Republicans win next November, Mr Obama may find that he doesn't own that war anymore, as Congress tries to chip away at his authority in the lead-up to the 2012 elections.
The repercussions of the current polarisation will endure well beyond November if the Republicans gain majorities in the House and Senate. Bipartisanship has long been a pillar of American foreign policy, the notion that American differences end "at the water's edge". Mr Obama restored harmony after the acrimony of the George W Bush years. But with so much at stake in Washington, that hiatus may have just ended.
Michael Young is opinion editor of the Daily Star newspaper in Beirut