A year before Mitt Romney picked him as a running mate, Paul Ryan gave a speech in which he discussed the promise and peril of the Arab Spring. "It's too soon to tell whether these revolutions will result in governments that respect the rights of their citizens or in one form of autocracy…supplanting another," he said. "While we work to assure the former, American policy should be realistic about our ability to avert the latter."

More generally, Ryan said, "American policy should be tempered by a healthy humility about the extent of our power to control events in other regions." It was hard to discern any such reticence in this week's presidential debate, during which Romney agreed with President Obama that the U.S. government has a duty to liberate and pacify the world, by force of arms if necessary.

I say "debate" because that is what they called it, but there was almost no disagreement about the ends or means of U.S. foreign policy. "I absolutely believe," Romney said, "that America has a responsibility and the privilege of helping defend freedom and promote the principles that make the world more peaceful." Obama agreed that "America remains the one indispensable nation, and the world needs a strong America."

That may sound flattering to American ears, but to many people around the world it has the ring of arrogance. "If we're an arrogant nation," George W. Bush warned during the 2000 presidential campaign, "they'll resent us."

Back then Bush presented Republicans as less meddlesome than Democrats. He recommended a more "humble" foreign policy and expressed disdain for nation building, saying, "I'm not so sure the role of the United States is to go around the world and say, 'This is the way it's got to be.'"

Obama and Romney are. "We have to help these nations create civil societies," Romney said. Obama concurred, even while incongruously declaring that "we can't continue to do nation building in these regions."

As Bush did after 9/11, when he launched two enormously expensive nation-building projects in Iraq and Afghanistan, Romney and Obama rationalize American intervention as necessary to prevent terrorism. To discourage violent extremism, they say, we must encourage democracy, the rule of law, equal rights for women and religious minorities, free markets, economic development, and strong educational systems.

These are all good things. But that does not mean it is the U.S. government's proper function to accomplish them in other countries, and the attempt to do so can backfire, feeding the resentment that fosters terrorism and empowering its perpetrators.

Consider the Syrian civil war. Romney and Obama agreed that the U.S. should organize the rebels and arm them, either directly or by proxy. Although they promised they'd be careful not to help America's enemies, so far most of the weapons supplied to the opposition have ended up in the hands of Islamic extremists.

Romney said he sees no need for direct military intervention in Syria "at this stage." Obama said "for us to get more entangled militarily in Syria is a serious step." But neither of them ruled it out, and this is where the logic of overthrowing tyrants to make America safe from terrorism leads.

Perhaps recognizing that reality, Romney wants to boost military spending, even though, as Obama noted, we already "spend more on our military than the next 10 countries combined." Romney poses as a fiscal conservative, claiming he wants to eliminate every program "we don't absolutely have to have." Yet when it comes to military spending, he is completely unwilling to prioritize, insisting that any "cuts," even if they only amount to a slower rate of growth, would be "devastating."

The grotesquely bloated military budget that Romney supports is not necessary for defense, unless you define that function so broadly that it requires policing the planet. Republicans are supposed to be skeptical of government's competence and wary of unintended consequences. Unfortunately, that skepticism stops at the border.