When evil is eradicated in one place, the spiritual impact is felt around the world.

וּרְגָמָהוּ כָּל אַנְשֵׁי עִירוֹ בָאֲבָנִים וְמֵת וּבְעַרְתָּ הָרָע מִקִרְבֶּךָ וְכָל יִשְׂרָאֵל יִשְׁמְעוּ וְיִרָאוּ: (כ"א כ"א)

"All of the men of his city shall pelt him with stones and he shall die; and you shall remove the evil from your midst; and all Yidden shall hear and they shall fear." (21:21) The question arises: If the transgressor is executed here, how will all of Klal Yisrael hear? The answer can be that this is one of the secret workings of the world which we cannot understand rationally: When evil is eradicated in one place, the spiritual impact is felt around the world. Harav Moshe Teitelbaum (1759-1841) the "Yismach Moshe" comments on this Posuk: If you want that all of Klal Yisrael should hear your rebuke and mussar and to fear Hashem, first eradicate the evil from within yourself. A similar episode occurred in Yerushalayim. One Shabbos after davening Hagaon Rav Yosef Chaim Sonnenfeld זצ"ל began a fiery drasha on Shemiras Shabbos. The elite of Yerushlayim asked why speak in this shul where everyone is strong in Shabbos? The Gaon answered if we will be stronger here, then other Yidden all over the world will also become stronger.