In the chapter on Tisha B'av in Rabbi Tzvi Leshem's book, "Redemptions," he explains that, essentially, we are in a middle state, whereby we-as an Am, not as individuals-can choose to either continue keeping this fast, or not. As he quotes from the Gemara (Rosh Hashanah 18b), "When there is peace, they [the days of fasting, including Tisha B'av] are for for joy and gladness, when there is government persecution, they are fasts, when there is neither government persecution nor peace, if [the Jews] desire they should fast, and if not, they should not fast."
There seems to be a strong consensus among commentators and halachic authorities that the main point of these four fast days is to bring us to teshuvah, as the Chofetz Chaim wrote, "There is no fasting, except as a preparation for teshuvah (Mishnah Brurah, Hilchot Tisha B'av V'shaar Taaniyot, 1: 1)," or in the words of the Rambam the fast is, "to arouse hearts to open to the ways of teshuvah (Mishnah Torah, Hilchot Taaniyot, Perek 5: 1)." While Rabbi Leshem goes in the direction of establishing considerations of social justice as a yardstick for determining when we have truly made teshuvah, I believe those issues to be secondary, ones which will be corrected as a matter of course by people whose consciousness of G!d becomes all-encompassing.
In Likutei Halachot (Hilchot Taaniyot, Halachah 1), Rabbi Natan links our loss of malkut, kingship, to a lack of emunah, and says that we fast in order to strengthen our emunah which will thereby bring back malkut to Am Yisrael, alluding to the coming of the Messiah and rebuilding of the Temple. Of course, strengthening one's emunah is not a contradictory goal from 'making teshuvah.' Part of returning to G!d is having 'faith' in G!d. But what exactly does Rebbe Natan envision us achieving in our emunah? After all, treating each other justly may be observed and measured, but belief is much more slippery, it is a state of consciousness. A few sections later (Halachah 3), Rebbe Natan gives the insight that, when one has emunah shlemah, total emunah, one knows that all is from Hashem, and therefore there is no such thing as hardship and lacking.
One might make the mistake of thinking that this consciousness should lead one to be passive in the face of suffering. After all, if G!d is in the suffering, if G!d has willed that the poor person be poor, and the sick person be sick, and the war-torn nation be war-torn, why should we do anything to change the situation? However, as Jews we have the Torah and mitzvoth, and part of seeing G!d in everything is seeing that he is making demands of us, testing us, begging us to draw closer to him by doing the right thing. Our feelings of lack and want are true, are 'godly,' and are placed there by Hashem for a reason. It is with this dialectic consciousness, going back and forth between realizing Hashem's presence in everything, and that Hashem Himself wants us to perceive shortcomings and to fix them, that we draw closer to the Creator. The Torah abounds with proof of this, including many mitzvoth, such as: treating your fellow like yourself, giving tzedakah, returning the beged (garment) to someone it was taken from as collateral at the end of each day, ad infinitum. Obviously we are not meant to ignore or, G!d forbid, allow injustice and suffering to continue under the guise of G!d-consciousness, but rather to take our consciousness of G!d's presence in the difficulty to drive us, even more so, to fix the apparent lack with gusto and with alacrity. The homeless man's poverty is not a matter of chance, but a divine call to action. Every chisaron (lacking) is created just to help us come closer to Hashem by fixing it. The life of Rebbe Nachman itself exemplifies this sort of 'activism,' albeit primarily on a spiritual level. He was constantly traveling and working, all to help others to rise to a higher spiritual level, saving many from spiritual death by teaching them how to create a personal relationship with the Creator.
In other words, when we recognize that "There is none other than him"(Ain od milvado), and "There is no place empty of him"(Leit atar panui minay), when we truly recognize G!d's presence in both our apparent hardships as well as our triumphs, our loss as well as our gain-and follow the practical implications of that consciousness by allowing it to spur us to action-then we will merit the return of G!d's revealed presence in the world, in the rebuilding of the Holy Temple and the re-establishment of the Davidic dynasty. May it be soon and in our days.