To fund its debt Japan had to export goods, while the US merely exports dollars. If the unthinkable should occur and the dollar is replaced by a basked of currencies, or the IMF creates a totally different system of credits etc. Then the US economy will obviously be affected negatively.

            2010 And Beyond - Deflation Japanese Style Synopsis: today Jan 16, 2010 Nikkei 225 same as 1987. Price levels now are about 25% of what they were 20 years ago. S&P to the Nikkei 225 has carted the same course since 1980.  Current (as of Jan 16 2010) market has upside potential. Bear markets take a long time to correct. 1929 took up to 1953 to correct.  Japan market boom accompanied property boom. Market in Japan collapsed in 1990. Japan then cut interest rates to zero in 1999 through 2006. Japanese government tried one bailout and stimulus after another.

            Today Japan is mired in deflation, unemployment rising and recovery loosing ground. Hatoyama government is increasing the deficits to keep from tipping over completely.

            Differences between Japan and the US: Japanese people were saving throughout, while Americans are broke.  Japanese economy continued to produce and export. US has a large trade deficit and no end in sight.  The Yen is rising against the Euro and Dollar. That is not good for exports from Japan.  Globally we are at rock bottom. Once short term interest rates begin to rise long-term will follow. Long term bonds are on the rise already.