Typically, several factors determine the level of American support — whether the nation we’d theoretically be fighting against is seen as a threat to American interests, whether we’re allies with the country we’d be supporting and whether respondents feel the war would be successful with few casualties, Smeltz said. Americans see Russia as a threat and Ukraine as an ally, but it seems that many Americans think a war with Russia would not be quick and easy, which could explain many Americans’ hesitancy over sending troops.

Americans also typically support actions like diplomacy and air strikes more than sending troops to war. Other factors, like where in the world a conflict is, or which party the sitting president belongs to, don’t register as important in polls, Smeltz said.

But whether and how Americans favor U.S. involvement in foreign conflicts aren’t the only lessons from Afghanistan and Iraq. Tanisha Fazal, a political scientist at the University of Minnesota, said modern military medicine has also altered how we should calculate the cost of war. More soldiers are surviving battlefield injuries, but they’re coming home wounded. Fazal said that hasn’t changed how most Americans think about sending troops abroad — except for people who are caretakers of those who came home wounded. “They know that they’re going to be paying the cost of war,” she said.