but this isn't really the point, you should compare Players of the same Quality like Nash and Kidd in Canada or Nowitzki and garnett in Germany(i hope this comparision is ok, i am not that good in the NBA).
At least i think the biggest diferences are in the weak players, where nationals(or in NBA relations regionals from a nearby university) should have more attetion then a foreigner. At least i could tell, tell nearly no one would buy a Crouch jersey(untalented SG/SF backup from america in the basketball team from my home) but i know some who got some from Wysocki(young german talent, wesignedt at the same time) even if he weaker then crouch and plays less. Maybe germany is an extreme example, because in our league nearly all palyers are from other country(mainly america) but if i look at the roosters of my opponentsat the beginning of the season i could nearly say the same about it here.