I think it all depends on how fast Nissan's wants to enter the U.S. small-car market.
If they want to do it now, they have the current Platina (Mexico), Cube, March, Micra, and Moco. If they want to do it by the end of the year with brand new product, they can use the Tiida, Tiida Latio, or Note. If they can hold off for a bit, they can bring in the next generation Cube.
Personally, I'd like to see the Cube here and one of the other models, like the Tiida or Tiida Latio.