I gather that one of the reasons why the desecration continues is because there's no way a person can rectify the chilul Shabbos in the future, because, well...he's dead! Rabbeinu writes in רעז that the tikkun for desecrating Shabbos is through achila for the sake of Shabbos. A dead person cannot eat during any forthcoming Shabbos, and therefore it can't be rectified atleast in this world. But what about ochel ruchani? Could that rectify the desecration of Shabbos caused by a Jew's death? And, who actually desecrates that particular Shabbos when the Jewish soul departs this world? Is it the individual or all of Knesses Yisrael?
Regardless, the beauty of Reb Nosson's words lies in the fact that he stresses how important it is that the Jews recieve Shabbos. If the Jews were to foresake Shabbos, she would not only have no pair, but her intrinsic holiness would be neglected and ignored completely, because "Hashem didn't give it to the other nations." Shmiras Shabbos is solely up to the Jewish people, and kabbalas Shabbos depends on every single Jew.