Russia’s annexation of Ukraine’s Crimea should be a reminder that NATO is still most relevant for what it set out to do in the first place — keep the Russians out of Europe.

Navel gazing about NATO’s future has been the favorite pastime of Atlanticists for more than twenty years. The collapse of the Soviet Union in 1991 seemingly robbed the alliance of its raison d’être. “Out of theater” operations on the scale of Afghanistan — where NATO commanded more than 100,000 soldiers — are unlikely to be repeated. Many European allies have decreased their troop numbers there ahead of a 2014 deadline or pulled out altogether, prompting familiar complaints from Americans that the Europeans aren’t doing their fair share.

Former American secretary of state Hillary Clinton warned that the alliance might “slide into military irrelevance.” Robert Gates, the former defense secretary, warned that Americans’ “emotional and historical attachment” to NATO, strong during the Cold War when the West was united against the Soviet threat, was aging out. Future leaders, he predicted, “may not consider the return on America’s investment in NATO worth the cost.” Foreign Policy‘s David Bosco fretted that that NATO could end up “a strategic backstop that exists just in case.”

Certainly the Europeans have shown limited commitment to the alliance. Only six European NATO members spend the required 2 percent of their gross domestic products on defense or more: Bulgaria, Estonia, France, Greece, Turkey and the United Kingdom.

America’s share of total NATO spending, by contrast, has risen since the end of the Cold War, from roughly 50 percent before the Soviet Union collapsed to more than 75 percent today.

Repeated European defense reductions are in part to blame but so is increased American defense spending in the wake of the September 11, 2001 terrorist attacks. The military’s budget grew from $291 billion that year to an $880 billion high in 2010, including financing of the war effort in Afghanistan. The Europeans could not, and had less reason to, keep up.

The United States also used NATO as a means to cloak their foreign policy in multilateralism which put an unreasonable burden on the European allies. NATO is less a tool of military adventurism for them than a guarantor of security in Europe, especially for the former communist states in Eastern Europe that regard warily Russian interference in the region. These states have altogether been more enthusiastic to support NATO operations afar because they need something in return. Western Europe faces no immediate security challenges. If there is a waning “emotional attachment” to the alliance, it must be there.

If America expected NATO to morph into a global police force, Russia’s seizure of the Crimea should definitively put such ambitions to rest. Rather the alliance is fulfilling its traditional goal of reassuring allies on Russia’s border and deterring Russia from making more territorial demands in Europe.

If the Americans don’t see why they should disproportionately contribute to this effort, it is only because Russia’s strategic ambitions are no longer global but confined to Eurasia. And if it means NATO exists “just in case” — well, isn’t that the very point of a defensive alliance?