I hope I don't sound too much like a Pollyanna when I say that, looking back with the detachment of history, future generations may very well wonder what the American people were ever concerned about when we fretted over keeping our global prominence.
Japan scared the daylights out of us in the 80s and early 90s, but we don't utter a peep about them anymore. (Although it's interesting to note that they're still not far behind us at productivity, GDP, etc.).
Now we're just as fearful of China. On one hand, it's easy to see why, as they're growing at such a mind-boggling pace. But legions of their people still starve to death every day - starve, as in die of empty bellies! How can a nation in such straights maintain its self for long? China's competitive edge is propped up by an artificially-weakened currency and cheap labor, which is already rising in price and fueling transfer of jobs to less expensive nations such as Vietnam. And corruption is so endemic in China that it's hard to argue that they have the #1 guarantor of economic success, the rule of law.
Of course, we could also fret over the EU's new prominence if we choose. Maybe, if something happens in China's economy, that will be our next hobgoblin.
Here's the part I find fascinating about American culture, though: our entire history, about 400 years worth, is the story of simultaneous decline and rejuvenation. Yes, we have life-sapping American Idolatry, lazy, uneducated, pierced twenty-somethings, and rampant teen parenting. These factors are degenerating our society - they are, without a doubt in my mind!
But at the same time there are plenty of kids who are starting businesses, dedicating themselves to philanthropy; getting advanced degrees. I just met yesterday with a 30-year-old who, all by himself, is compensating for 20 slackers. It's hard to be a pessimist after an hour with a guy like that.
This country continually regenerates its self. America remains the most vibrant culture ever. And it will as long as enough of us care to ask the question, "Is this country in trouble?" I don't think that question will ever go away.