General economy
USA has high trade deficit: especially with oil producing countries and manufacturers like China.
GDP Growth is much lower than in emerging economies: 0-3%.
Industry
USA’s industry is highly innovative - one of the best in the world. Industries are highly mechanized.
Manufacturing
America is the biggest manufacturer of goods in the world. But, much of the manufacturing is done in highly automated factories which are run by a handful of skilled employees overseeing the automation; manufacturing involving low skilled labour has moved to countries (in the developing world) with cheaper labor.
Public debt, consumption
Public debt (not same as government debt) is high (as of 2007-2011): so the consuming power of the population is likely to decrease.
Decreasing income for many
The classic ’American dream’ includes the hope that with each succeeding generation, the standard of living (esp household income) improves. But, household income has actually been decreasing since 1970’s; but the decline was made less noticeable for a few decades due to easily available loans.
For a while, many people masked their declining income using easily granted debt.
Low unskilled labor opportunities
Historically, there were two ways in which one could attain a good standard of living - by entering the skilled-workforce (mainly in the service industry) after getting good education; and by entering the unskilled factory workforce. The latter option has ended due to the automation and off-shoring in the manufacturing industry. According to several studies, the most promising way of solving this seems to be to offer kindergarten training to ensure that kids acquire sufficient social skills!
High expenses
Another problem is the rising cost of medical care - the root of which problem probably lies with the fact that employers are incentivized to purchase and offer medical insurance to people.
Government debt
As of 2011, it is at 100% of GDP: Historically, when deficit 90%, nations’ economies tend to decline.
Deficit and response
Tax rate is too low to pay for the local, state and federal government expenditures.
Political deadlock
A part of the population, particularly the Republican party supporters, favor a lower level of public service and lower taxation, further they don’t even favor a higher taxation rate for the rich (a response which stems from socialism-phobia and the unrealistic hidden American dream of the non-rich that they will be rich one day).
Another part of the population, supporting the Democratic party, wants higher taxation and maintenance of good government services.
These factions are unable to reach a compromise as of 2011.
Lenders
Government debt is high: with many trade-partners (esp: China, Japan) lending back the excess dollars they get due to the trade surplus. For reasons why they do this, consider the case of China described elsewhere.
Dollar
Much currency is in foreign hands due to USAs’ trade deficit. Also, in response to the credit crisis following the sub-prime mortgage crisis of 2007, the Fed devalued the dollar by printing trillions of dollars.
So, dollar is likely to fall in value relative to other currencies, especially Yuan.