Greece has zero NBA players! Kudos to them.
It's hard to get a US team together when the players are each superstar multi-millionaires. They are all used to be being pampered on their home teams, and then they have to become one among many. Besides, it's clear the US players core skills are eroding in favor of the slam dunk and TV highlight moves. They can't defend a good pick-and-roll move at all, something that's taught from what, third grade?
I see the same phenomenon with soccer. The national teams can be beaten by a top rate club team, and often are in friendly games.