Not a lot to do with the Nissan badge, in The U.S.A sales of The Zed series held up much better than The Z4 or The Audi TT, only Porsche did better. 
  
Cars Sold in The U.S.A 
  
Z4...........2004.......13,654, 2009..........3,523 
  
350/370..2004........30,960, 2009.........13,118 
  
Audi TT...2004........5,275, 2009............1,935 
  
Porsche..2004.......31,473, 2009..........19,696 (Total sales of all Porkers) 
  
Maybe our American cousins don't have the same badge snobbery as us though. I will attempt to dig out further sales figures when I get a spare few hours. 
  
  
Pete