Welcome to Flyertalk,
BlakePaigeStone.
Unfortunately, there is no way to transfer US miles to NW.
However, even if you don't want to fly US you can use your US miles for a partner award -- United, Lufthansa, and Qantas all come to mind. And when USAirways joins the Star Alliance (likely next year) you'll have even more redemption options.
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View from the Wing: A blog about Free Miles and Free Markets