Apparently the International Olympic Committee has approved 3 on 3 basketball as a new competition for the 2020 olympic summer games. Below is a link from Sports Illustrated attempting to compile the best teams from each country.
Naturally, the USA has a ton of players to choose from, but I would imagine the best players (Lebron, Durant, etc) do not play -- Australia, led with Ben Simmons and Dante Exum, could be formidable.