Ramban (Tazri'a 13:47) writes that the punishment of tzara'as described in Parshas Tazri'a was a miraculous manifestation of Hashem's hashgacha, not a natural disease, and therefore, even though it is not a mitzvah hatelu'ya ba'aretz, it only occurred in Eretz Yisrael, the "nachalas Hashem," where Hashem's presence is most manifest. The Ramban continues and writes l'halacha that tumas tzara'as on houses did not apply until after the fourteen years of conquest and division of Eretz Yisrael by Yehoshua were completed. If you stopped reading there you might guess that this din is related to the previous idea. Since the kedushas ha'aretz was incomplete until after the fourteen years of kibush v'chiluk, as we see, for example, from the fact that terumos and ma'asros did not apply until after that fourteen year period, you might guess that the halachos of tumas tzara'as follow the same pattern and are absent when a full kedushas ha'aretz is absent. But that's not what the Ramban says. The reason nigei batim did not apply during those fourteen years is because to witness the hashgacha of Hashem in an open and revealed way requires having a tremendous degree of G-d consciousness. You have to be thinking of G-d and aware of his presence to deserve to see its effects. Such a high mental state of awareness is impossible while one is simultaneously engaged in fighting a war.
A long time ago we discussed (here and here) Rav Soloveitchik's idea that there are two dinim in kedushas ha'aretz: 1) The sanctification of the land through conquest (by Yehoshua) or chazakah (by Ezra) on our part, which served to define the boundaries in which certain agricultural mitzvos and mitzvos hateluyos ba'aretz applied; 2) The sanctity of the land as that place chosen by G-d as special. I think we see this distinction reflected in this Ramban. Nigei batim apply only in Eretz Yisrael because of that second type of sanctity which the land has -- it is Hashem's chosen place -- irrespective of how and when we are mekadesh it through our efforts. Therefore, the Ramban must invoke a psychological explanation as the basis for the din of nigei batim applying only after the fourteen years of kibush v'chiluk, as it has nothing to do with whether that first type of kedusha exists yet or doesn't.
Ibz Ezra (14:33) also writes that nigei batim only apply in Eretz Yisrael, but he explains the reason is because "godel ma'ales ha'aretz ki hamikdash b'tocham v'haKavod b'toch hamikdash." I'm a little confused by his meaning. Kedushas hamikdash and kedushas ha'aretz are two different things entirely. Eretz Yisrael had kedusha even before there was a mikdash; according to the Rambam, even when kedushas ha'aretz was nullified, kedushas Yerushalayim, the makom mikdash, remained intact. Why does Ibn Ezra need to invoke the importance of the mikdash as the place of Hashem's presence as a justification for the significance of Eretz Yisrael in this regard -- doesn't the kedushas ha'aretz stand as significant in its own right? Perhaps he is simply giving a siman, not a sibah, i.e. the kedushas ha'aretz does have independent significance, and one indication that this is true is the fact that the land is the makom mikdash, where the Shechina is most manifest.
I would probably have done this post anyway, but I made a point of putting it up now because I don't see how you can not spend 5 minutes tomorrow, 5 Iyar, not thinking about and pausing to appreciate the ideas of kedushas ha'aretz, appreciating the land which is "nachalas Hashem," appreciating the tremendous gift we have been afforded. It would take another whole post to fully discuss, but my opinion for what it's worth is that to simply dismiss the day as a political event with no religious meaning is completely off the mark. Can anyone truly doubt that the hashra'as haShechina of Eretz Yisrael is enhanced not only by the limud haTorah that goes on there, which is of course important, but also by the land being under autonomous Jewish control, no matter what degree of religiosity the government currently is at or not at? So whether you say hallel or don't say hallel, whether you do baha"b or say tachanun or whatever -- these are technical details -- take a moment to at least have a thought of hakaras hatov for what we have. Just think of the thousands of Jews across centuries of history who wished they were in our shoes, having the freedom and kedusha of Eretz Yisrael accessible just a plane ride away.