>How much of the US government debt is own by foreign holders?
About 34%
>How is this distributed around the world?
Not really known. There's reasonably good data on who buys it initially - though purchases by an offshore hedge fund will show up as an offshore asset, even though the real owners may be in New York or Palo Alto - but as they're bought and sold, the holdings are reshuffled in ways no one knows for sure.
You can bet that central banks of countries with big foreign reserves - Japan, China, Taiwan, etc. - have big Treasury holdings
Doug