FROM THE beginning of the Syria crisis almost three years ago, the Obama administration has found reasons to remain aloof. Every option for U.S. involvement — arming moderate rebels, enforcing a no-fly zone, carving out humanitarian corridors — entailed risks. But every imperfect option for action must be weighed against the risks of inaction: What happens if the United States fails to help shape or contain a dangerous situation? In that framework, it’s instructive to look at just one day’s news from the region:

●Syrian government helicopters on Monday dropped “barrel bombs” on residential neighborhoods in the nation’s largest city, rebel-controlled Aleppo. The bombs “are typically packed with screws, scrap metal, old car parts, blades and explosives,” an activist told the Wall Street Journal. Scores of people were killed, including at least 28 children.

●In Geneva, the United Nations launched an appeal for a record-setting $6.5 billion to help Syrians who have lost their homes and livelihoods and are being starved by government forces. In a nation of 22 million people, 8 million are in need of humanitarian assistance, Valerie Amos, U.N. undersecretary general for humanitarian affairs, said.

“As we look towards the fourth year of this appalling crisis, its brutal impact on millions of Syrians is testing the capacity of the international community to respond,” Ms. Amos said.

●The Post reported that extremist factions allied with al-Qaeda, which now control swaths of Syrian territory, are training children as young as 10 as combatants.

“This is the future threat,” one expert told The Post’s Joby Warrick. “These are the children of al-Qaeda.”

In Iraq, “suicide bombers and gunmen killed scores” as that nation tipped back “into its deadliest levels of violence in five years,” Reuters reported. Iraq’s regression has numerous causes, including the prime minister’s intransigence and President Obama’s withdrawal of all U.S. troops, but no factor looms larger than the spillover from al-Qaeda’s growing presence in Syria.

Al-Qaeda-inspired violence also spread westward, the Wall Street Journal reported, as “Sunni extremists have stepped up attacks on the Lebanese army . . . undermining the army’s attempts to assert its authority around the country.” The United States has spent $1 billion trying to bolster that army since 2006, the Journal noted.

●As far away as Bulgaria, an influx of Syrian refugees is fueling resentment and the rise of far-right, nationalist political forces, PBS’s “NewsHour” reported.

A day’s gleaning from the U.S. press inevitably leaves out many issues: the strains imposed on Lebanon, Turkey and Jordan by hundreds of thousands of refugees; the imperilment of Syria’s Christian minority; the irreparable loss of archeological sites and centuries-old mosques and souks, and more. Still, the litany of one day is sobering enough.

It’s impossible to know what U.S. leadership could have achieved, but it’s hard to imagine a more frightful outcome. The one advantage of inaction seems to be the ability to disclaim responsibility: We didn’t break it, so we don’t own it. Even that benefit, however, may prove transient. Already the United States is the largest donor of refugee aid. As misery spreads and anti-American radicals plant roots, the Obama administration, or its successor, may find that the costs of non-involvement far exceed those that would have come with timely and measured intervention.