Victor Davis Hanson:

In the last 60 years, we have been warned in succession that new paradigms in racially pure Germany, the Soviet workers' paradise, Japan Inc. and now 24/7 China all were about to displace the United States. None did. All have had relative moments of amazing success -- but in the end none proved as resilient, flexible and adaptable as America.

That brings us to the United States' greatest strength: radical self-critique. We Americans are worrywarts, always believing we're on the verge of extinction. And so, to "renew," "reinvent" or "save" America, we whip ourselves up about "wars" on poverty, drugs and cancer; space "races;" missile "gaps;" literacy "crusades;" and "campaigns" against litter, waste and smoking.

In other words, we nail-biters have always been paranoid that we must change and improve in order to survive. And thus we usually do -- just in time.