This is some interesting speculation:  The Once And Future Republic. A cogent excerpt:

The fact is that the remnant Lilliputian West has long depended on the Brobdingnagian stature and power of the United States to ensure its solvency, security, and ultimate survival. Absent the United States, what we like to call Western civilization would long ago have become a diorama in the vast Museum of History to pique the interest, perhaps, of Chinese high school excursions. And this is why, naturally, everybody loves to hate Americans, those “ignorant cowboys” and “loud vulgarians” whom Europeans affected to look down upon, those “rude mechanicals” that a vanishing breed of Brit, remembering Shakespeare, might have thought, those presumably aggressive conquistadors that so many Canadians, especially under the tutelage of former Liberal Prime Minister Jean Chrétien, smugly enjoyed dismissing as irredeemable barbarians and moral inferiors.

Envy and resentment of this sprawling and robust — and necessary — giant among the nations were the motivating factors. For without the brawny presence of the United States in the Hobbesian jungle of world politics, neither Europe, Britain, nor the former Commonwealth dominions, as I have argued, could have defended their Enlightenment heritage or relied upon their own feeble military resources to guarantee their longevity. Gratitude, however, does not come easily. Contempt and self-infatuation are far more attractive emotional reactions for the parochial accessories of the grand historical drama. All those in the West who picket American embassies, deplore American ambition, write anti-American articles, columns, editorials and books, and cry “Down with America” are precisely the sycophantic beneficiaries of American strength and munificence.

Be careful what you wish for, as the old adage has it. Europe, for example, responded with unadulterated joy to the election of a statist, far left American president who apologized for American exceptionalism, adopted the socialist model of governance, pledged to reduce military expenditures, and brought his country to the brink of bankruptcy. Europeans did not realize — or did not want to acknowledge — that their “advanced” socialist experiment in welfare governance depended in large part upon American military spending for the continent’s defense, which permitted a liberated fiscal surplus to be invested in social programs, early retirement benefits, and a cradle-to-grave security network.

It’s beyond doubt that America has some serious issues to deal with.  Fiscal insolvency, a devalued currency, a weakened military, a tax policy that is discouraging businessinvestment and growth, a failed education system – but we have a lot of strengths as well.  We still have vast natural and human resources, we still have a vibrant private sector, even taking into account the downturn of the past 24-30 months, during which time our economy has been lurching along like a 1939 Ford with a blown head gasket.

I’m an optimist.  We have time to turn things around.  But that time is not unlimited – we’d best get cracking.