Lt. Col. Stephen Coonen has an interesting piece in the US Army War College journal Parameters on the widening military capabilities gap between American and European forces. He argues:

The improbability of many European states committing more of their treasuries toward defense suggests that capabilities will continue to diverge. While this is certainly not a desirable condition, it is far from being the apocalyptic end of the alliance. The capabilities gap, while growing, has not led to a dysfunctional alliance. Rather, Europe’s and America’s leaders continue to acknowledge the enormous value and importance of the transatlantic partnership in advancing their shared values and facing their common threats. Despite recent strains in European-American relations, NATO continues to serve as a valuable organization that binds the allies together, providing the vehicle for continued cooperation. In this light, the military capabilities gap between the United States and Europe, as it exists today, is not as significant as many observers state or imply.

Still, NATO is a military alliance that has been engaged in the Balkans and is now much more active in Afghanistan. There’s a remote possibility it could be operating in Darfur in the coming months. And other crises may erupt at any moment (think southern Lebanon) where a robust NATO/European force may be needed –- which is why it’s hard to imagine that NATO will remain a healthy alliance in the long run with European governments devoting so little to their defense capabilities.