Should Japan write off US treasury debt?

From Bloomberg:

Japan should write-off its holdings of Treasuries because the U.S. government will struggle to finance increasing debt levels needed to dig the economy out of recession, said Akio Mikuni, president of credit ratings agency Mikuni & Co. The dollar may lose as much as 40 percent of its value to 50 yen or 60 yen from the current spot rate of 90.40 today in Tokyo unless Japan takes “drastic measures” to help bail out the U.S. economy, Mikuni said. Treasury yields, which are near record lows, may fall further without debt relief, making it difficult for the U.S. to borrow elsewhere, Mikuni said.

Wow. I'm rather speechless. What troubles me for Japan is at least two things. First, Japan's government shouldn't be responsible for the American government's profligacy. Second, even if Japan's government wants to save the American government from its own profligacy, I doubt this is possible. I trust neither the governments of Japan or America to do what is best for their own people. Instead, I expect them to do a great deal of damage in an attempt to preserve the status quo. For now, the best we can hope for in either country's government is gridlock. In the near term, I think gridlock is more possible in Japan than America.