The post-Cold-War era has never seen anything like what has come to be called “Ukraine,” and it will take time to absorb its meaning and effects.

For starters, those of us who labor in the trenches of the culture wars tend to think tech and its media platforms on balance are corrosive and toxic. And they are. But we need to acknowledge that those same messaging forces—which quickly assemble group thinking on a massive scale—here put in motion something powerful and potentially good.

Will the response stop Mr. Putin? Who knows? But it might, if we posit that the solid building block for this broad effort to resist is Ukraine itself—the unexpected ability of the country’s military to counter the Putin blitzkrieg and its people’s refusal to surrender.

Modern media like YouTube and Instagram helps create tissue-thin celebrities and “influencers.” Here the platforms instantly elevated Mr. Zelensky, a professional comedian, into a heroic influencer motivating his own people and tens of millions outside his country. When is the last time every member of the U.S. Congress stood to applaud a president?

The world’s behavior suggests, for the moment anyway, that we’ve decided that we’re all the North Atlantic Treaty Organization now, bound by a kind of global Article 5: A massive unprovoked attack on one of us is an attack on all of us.