It's not a hape for the USA, it is that all sports are organised in a different way. All top basketball teams are clubs, sport clubs which were small when they started and have grown. There are no franchises. All the teams have their tradition, their national league, their rivarlies etc etc. I don't think that a fan of Barcelona would like his team to play all year against the Hornets, the Raptors
and the Celtics instead of Real,TAU,Valencia,Malaga and Jovedut. Playing against NBA teams is nice for pre-season games but I don't know if there would by any team to leave its national championship to play in the NBA.
And I think that when they talk about NBA expansion they mean to bring the existing teams to the league (Real Madrid,Panathinaikos,Barcelona,CSKA,Maccabi) not to create to franchises ex. Madrid Desperados, Russian Bears, Rome Ceasars etc.