Tisha Ba'v is all about reflecting on the things that prevent the Jewish people from becoming their full potential. Remember that one of the things that happened on Tisha Ba'v was the sin of the 12 spies, and the refusal of Bnei Yirosel to go into Israel. Fasting because there are many Jews abroad who don't feel enough of a connection to come to Israel is very similar.
U.S. says working on initiative to de-escalate Syria fighting, with focus on Aleppo (Reuters)
from the article: It is wrong to fast on Tisha B'Av?