Whenever and wherever there are peaceful, equipoised devotees who are well behaved and decorated with all good qualities, that place and the dynasties there, even if condemned, are purified. (SB 7.10.19)
According to this verse, ghastly cities such as London, which Prabhupāda personally certified as “hellish,” New York, Tokyo, Sydney, and many others are now purified. Because Śrīla Prabhupāda touched his divine lotus feet thereupon, they have all become tīrthas—at least the specific portions to which he went.
The Vedas enjoin that mlecchas should not even be seen by cultured people. But the Westerners who came to Prabhupāda are no longer mlecchas. They are now Vaiṣṇavas capable of purifying even high-caste brāhmaṇas.