HARRISBURG, Pa. — A few months ago, Kevin Kinard, a 55-year-old utility worker here, had barely heard of the Islamic State in Iraq and Syria. But when the Sunni militant group beheaded a second American journalist, Mr. Kinard clicked on an Internet video of the execution — and lost sleep for two nights.  “Nobody wants war,” he said, taking a break from some underground streetlight switch work near the State Capitol here to explain why he believes ISIS must be destroyed, and why America must take the lead. “It costs too much money; it costs lives. But we are protecting ourselves. We can’t turn a blind eye.”  A half-mile away, in an artsy neighborhood of thrift shops and cafes, Mary Hess, 57, sat amid stacks of rare volumes at the Midtown Scholar Bookstore and offered the opposite view.  “What possible purpose for America,” asked Ms. Hess, a caterer, “would it serve to get us more in debt and to fight in Iraq and Syria?”  As President Obama makes his case for an aggressive American-led campaign to “degrade, and ultimately destroy” ISIS, he is confronting a confused, conflicted and in many ways exhausted nation.  In dozens of interviews around the country — in shopping malls, restaurants, small businesses, and on city sidewalks — and follow-up conversations after Mr. Obama’s address to the nation on Wednesday night, Americans expressed horror at the brutality of ISIS, alarm at its seeming emergence out of nowhere and fear that it is grooming agents in the United States.  But they also seemed deeply divided over Mr. Obama’s leadership, and unsettled at the thought of yet another conflict that could last into another presidency.  Mr. Obama called for expanding airstrikes but rejected sending combat troops to Iraq and Syria, where ISIS is seizing territory in its quest to build a caliphate, or Islamic state. Polls show most Americans support that course; on Capitol Hill, Democratic and Republican leaders are in rare agreement on it.  But conversations reveal feelings murkier than the numbers suggest.  “I don’t know if I’m ready to get into another war,” Clara Bush, 64, a science fiction writer, said as she picked through the aisles of a sprawling camping and hunting supply store in Colorado Springs, a deeply Republican city in an area that is home to five military installations.  Her voice shook slightly; she wondered what good airstrikes or sending military trainers would do. “America,” Ms. Bush declared, “needs to develop an isolationist platform. We need to take care of ourselves.”  A few aisles away, Chris Marsette, 45, a military contractor and Air Force veteran who served in Iraq in 2003, sounded similarly cautious, yet drew a different conclusion.  “We really don’t want to get bogged down in another war,” said Mr. Marsette, who faults Mr. Obama for “just sitting back” while ISIS grew. “Before it grows too big,” he said, “there has to be some kind of action.”  As the nation marks the 13th anniversary of the Sept. 11, 2001, terrorist attacks, the ISIS rampage in the Middle East is provoking thought about America’s place in the world. Hunched over his computer at a coffee shop in Harrisburg, Greg Beeman, 42, who telecommutes to his job at Nyack College in New York, said America’s greatness derived from its willingness to lead.  “There is always going to be evil in the world,” said Mr. Beeman, who said he voted for Mr. Obama in 2008 and Mitt Romney in 2012. “Someone has to address it.”  Perhaps nowhere are the memories of Sept. 11 as searing as in New York. Buying coffee on Thursday at a Forest Hills Starbucks, Martin Sandler, 57, grappled with the odd juxtaposition of the anniversary and Mr. Obama’s speech. “It’s hard to believe we’re back at this spot again,” he said.  In Los Angeles, Lawrence Shih, a county worker who describes himself as politically liberal, regards the last Iraq war as “a total mistake.” But he is appalled by ISIS’ attempts to eradicate the Yazidis, a minority religious sect. “We cannot let these people overwhelm regions and commit genocide,” he said.  On the campus of Northern Illinois University, in the small city of DeKalb, 65 miles west of downtown Chicago, Scott LaDeur, a visiting assistant professor, strayed from his syllabus in his class on global terrorism on Wednesday to explain the origins of ISIS. The 50-minute class produced a lively discussion, ranging from the threat to the United States (“On a scale of 1 to 10, probably around a 4,” said one student, Francesco Cimmarrusti, 21) to the wisdom of arming moderate Syrian rebels, as Mr. Obama has proposed.  Tapan Dave, who is 34 and studying public administration, fears such a move would increase the risk of a terrorist attack on American soil. “We should keep our hands out of the war,” he said, adding that American allies should take the lead.  But after listening to Mr. Obama, he softened a bit. “I think I’m convinced — kind of,” he said.  In a nation divided by partisan politics, the debate over military action does not track along partisan lines, though the debate over Mr. Obama’s performance does. That was evident on Wednesday morning in Marysville, Pa., a town of about 2,300 people across the Susquehanna River from Harrisburg, in heavily Republican Perry County.  At the local diner, where eggs, hash browns and toast were on special for $1.79 and the refrigerated display case featured shoofly pie, suspicion of the president ran deep. A waitress whispered that she likes Mr. Obama. But most patrons scowled at his name; some, in accusing Mr. Obama of being weak, conflated terrorism with Islam.  Terry Matter, a retired Army veteran and computer programmer, said it was time for Mr. Obama to “quit coddling the Muslims,” but added quickly, “They are not all bad.” A few tables away, Allen Taylor echoed the sentiment, over eggs and pancakes with his wife and two young children.  “He should have had troops in there a while ago,” Mr. Taylor, 47, a carpenter, said. “To me, it just seems like he kind of protects the Muslim people.”  Back in Harrisburg, Joyce Davis, communications director to Mayor Eric Papenfuse, a Democrat, is troubled by such talk. Ms. Davis is a former foreign correspondent, the author of two books on Islam and founder of the World Affairs Council of Harrisburg; she says people are frightened and confused. Even her pastor struggled to make sense of ISIS in a recent sermon.  “He was trying to see it from a spiritual perspective — demonic forces,” she said.  Chatting with friends at the Midtown Scholar Bookstore, Robert Lane, 70, a retired state employee, applauded Mr. Obama’s cautious deliberation, saying the time had come for America to act. “The beheadings,” he said, “have galvanized the country.”  At the State Capitol here, a granite bench bears a paraphrase from John Peter Gabriel Muhlenberg, the Revolution-era pastor and soldier: “There is a time to pray and a time to fight.” It caught the eye of a couple from Portland, Ore.: Steve Anderly, 67, an engineer, and his wife, Andrea, 65, a lawyer.  “It would be nice if we could pray our way out,” he said. To which she responded: “But sometimes we have to fight.”  The couple, Democrats, were here visiting Mrs. Anderly’s sister and her husband, Republicans. Though the four disagree on politics, all said ISIS must be stopped. Yet even as Mrs. Anderly wanted to “bomb the hell” out of the militants, she was uncomfortable with a protracted campaign.  “We’ve been doing this for 11 years. Another three years? We’re not supposed to be a war nation; we’re not Rome.”  If Mr. Obama intended to assuage American unease, he succeeded with at least one person: Mr. Kinard, the utility worker.  A Republican, he voted for the president, he said, and regrets it. But Mr. Obama’s speech impressed him; he found the president “clear and concise,” especially in explaining that ISIS did not emerge out of nowhere, but is the successor to Al Qaeda in Iraq — something Mr. Kinard said he had not previously grasped.  “For the first time, possibly since the elections, I’m pretty proud of him,” Mr. Kinard said.  Not so Ms. Hess, the caterer, a Republican who voted against the president. She came away unconvinced that Mr. Obama has “a clear, cohesive plan.” Instead, she posed a question that seems to be on many American minds after more than a decade of war:  “Did we really accomplish anything?”  Reporting was contributed by Julie Turkewitz from Colorado Springs; Mitch Smith from DeKalb, Ill.; Ian Lovett from Los Angeles; and Al Baker from New York.  A version of this article appears in print on September 12, 2014, on page A1 of the New York edition with the headline: Weary of War, but Favoring Airstrike Plan. Order Reprints|Today's Paper|Subscribe
Many Americans agree that ISIS is a threat to the United States, but many wonder whether the country should edge toward another war.