Putting the debt in U.S. dollars and possibly yen is smart and hedging the debt will limit currency fluctuations (note that un-hedged debt burnt many Thai corporates during the Asian crisis).
If the U.S. government temporarily misses a debt payment while promising to make bondholders whole as soon as the debt limit was raised, 10-year note yields would rise about 37 bp, according to the average estimate of 45 JPMorgan Chase (JPM) clients that it surveyed.