Connecticut Cuse is right that Towns can claim a US citizenship and join the US team for the next Olympics if he chooses so. Being from Jamaican heritage, I follow the track and field scene frequently and there have been plenty of athletes who participated for Jamaica, and then switched to the USA, UK, or Canada. So I don't see things being an issue for Towns and Hibbert if they wanted to join the USA team for 2016.
There is a 3 year waiting period before he can switch back to competing for the U.S....which should be no problem for the 2016 Olympics and beyond. The following comes from the bylaw to Rule 42 of the Olympic Charter.
1. A competitor who is a national of two or more countries at the same time may represent
either one of them, as he may elect. However, after having represented one country in
the Olympic Games, in continental or regional games or in world or regional champion -
ships recognised by the relevant IF, he may not represent another country unless he
meets the conditions set forth in paragraph 2 below that apply to persons who have
changed their nationality or acquired a new nationality.
2. A competitor who has represented one country in the Olympic Games, in continental or
regional games or in world or regional championships recognised by the relevant IF, and
who has changed his nationality or acquired a new nationality,
may participate in the
Olympic Games to represent his new country provided that at least three years have
passed since the competitor last represented his former country. This period may be
reduced or even cancelled, with the agreement of the NOCs and IF concerned, by the
IOC Executive Board, which takes into account the circumstances of each case.
