Even though America has been at war for over a decade and Iran is threatening to build a nuclear weapon, domestic issues have dominated this election, with President Barack Obama and Republican presidential nominee Mitt Romney focusing most of their attention on taxes, health care and the economy.

That is about to change as foreign policy and national security take center stage in Monday’s final presidential debate in Boca Raton, Fla., and last month’s attack on the U.S. embassy in Libya continues to raise questions about whether the Obama administration put Americans at risk by ignoring security warnings.

The killings of U.S. Ambassador Christopher Stevens and three other Americans has opened a Republican line of attack that was thought to be all but unthinkable a few months ago: that the sitting president who ordered the killing of the world’s No. 1 terrorist could be vulnerable on foreign policy.

Surveys show that more Americans trust Obama to handle foreign affairs than Romney, but the Republican challenger has hit Obama hard over the Libya attacks, and is pushing a campaign message that America would be stronger under a Romney administration.

The next president will have to contend with a broad array of international issues. Americans remain at war in Afghanistan, a civil war is raging in Syria in which 30,000 people have been killed, Iran’s plans to build a nuclear weapon have prompted talk of an Israeli pre-emptive attack, some al-Qaida’s affiliates are gaining strength, and officials worry about the possibility of cyber space attacks.

In addition, the European debt crisis threatens to damage the fragile economic recovery in the United States. Heather Conley, a former State Department official under President George W. Bush, said “the debt crisis is the most significant test the Europeans have experienced since the Second World War. We have not focused as closely as I would like on the political and social impact of the crisis on Europe.’’

“We talk a lot about the short-term economic impact, but I would like to hear more about the long term impact the debt crisis will have on NATO and our European partners,” Conley said. “The European debt crisis has been difficult for us to watch as it is a dim reflection of our situation here in the U.S. We face similar challenges.”

Obama has peppered his speeches with reminders that he removed all U.S. combat troops from Iraq and put a dent in the terrorist enterprise that planned the 2001 attack on America: “al-Qaida is on its heels and Osama bin Laden is dead.’’

Two-thirds of al-Qaida’s leaders have been killed during Obama’s presidency, largely because of an aggressive policy of using Predator drones to attack terrorist sanctuaries in Pakistan. Obama also supported transitions to democracy in Egypt, Libya and Tunisia.

“We’ve seen Obama’s policy – it’s effective, focused and he doesn’t make mistakes,’’ said former Army General Wesley Clark, who commanded NATO forces in Bosnia in 1999 and is an Obama supporter. “We haven’t seen Romney’s yet. There is a lot of rhetoric so far.’’

Romney has outlined a more assertive foreign policy, one that resembles the muscular approach employed by former President George W. Bush. He has pledged to dramatically step up military spending — including building 15 new naval ships every year — and take a tougher approach against Russia and its president Vladimir Putin.

He vows to increase defense spending.

Obama “hopes for a safer, freer, and a more prosperous Middle East allied with the United States,” Romney said in a speech this month at Virginia Military Institute. “I share this hope. But hope is not a strategy.’’

“We cannot support our friends and defeat our enemies in the Middle East when our words are not backed up by deeds, when our defense spending is being arbitrarily and deeply cut, when we have no trade agenda to speak of, and the perception of our strategy is not one of partnership, but of passivity,’’ Romney said.

In addition to Libya, Obama and Romney have clashed over how to bring an end to U.S. military involvement in Afghanistan. In the aftermath of the Sept. 11th, 2001, terrorist attacks in New York and Washington, U.S. and NATO forces toppled the Taliban regime that provided sanctuary to bin Laden and his al-Qaida allies.

But the war isn’t over. More than 2,100 American soldiers and 1,190 coalition troops have been killed since the U.S. first sent troops to Afghanistan, while most estimates put the number of civilian Afghans killed at more than 20,000.

Obama wants to withdraw all U.S. troops from Afghanistan before 2014, while Romney suggests pursuing a transition to Afghan security forces. He said that he will not “abandon the Afghan people to the same extremists who ravaged their country,” fearing that the Taliban would wait until the American departure before launching operations aimed at overthrowing the government in Kabul.

On some national security issues, the differences between Romney and Obama are cosmetic. Neither candidate wants to impose a no-fly zone to stop the fighting in Syria, and both are deeply reluctant to use military force to prevent Iran from producing a nuclear weapon.

But on other issues, there is a wide gulf. Romney has branded Russia as the “No. 1 geopolitical foe” of the United States, a contention Obama rejects. The Russians have rebuffed the U.S. by supporting Syrian President Hafez al-Assad. The Russians have criticized sanctions imposed by the European community and the U.S. in an effort to prevent Iran from building a nuclear device.

“I believe that Russia and the U.S.-Russian relationship will be a growing challenge for whomever is elected in November,” Conley said. “We know that there is a list of challenging issues, like Russia’s relationship with Syria, the growing concern and disconnect on human rights and democracy in Russia, missile defense and Russia’s relations with its post-Soviet neighbors.”

Obama and Romney also have engaged in a dispute on defense spending. While Obama wants to tighten the overall spending of the military to cut down the massive federal deficit, Romney wants to maintain defense spending at a minimum of 4 percent of the nation’s gross domestic product.

“There’s no immediate threat — Hitler is not building up his forces to invade America,’’ Clark said. Instead, he contended the major security challenges involve al-Qaida and cyber space.

“But I don’t hear Mr. Romney talk about that,” Clark said.

Today’s U.S. military is the world’s most powerful and America spends roughly 43 percent of the world’s military expenditures. According to the list of top 10 defense budgets in the world, the U.S. spends at least $100 billion more than the nine others — countries like China, Russia, England and France — put together.

Throughout this campaign, the issues of foreign affairs and national security no longer carry the same importance to voters as they did during the height of the Cold War when thousands of U.S. and Soviet nuclear tipped missiles were aimed at each other’s country.

A USA Today survey last week of voters in 12 key swing states — including Ohio — shows voters rated the deficit, federal debt and health care as more important issues than national security and terrorism. While 47 percent of women rated national security as important, only 37 percent of men said the issue was important to them in deciding which candidate to support.

“Americans, like everyone else, are more interested in what happens in their own country than in the rest of the world,’’ said Axel Dreher, a professor of international and development politics at Heidelberg University in Germany. “But we’re all interested in America.”