For most English speakers, “Mecca” has long been the accepted transliteration of the original Arabic for the holy city. The word Mecca in English has gone on to refer to any center of activity sought by a group of people with a common interest. Las Vegas, for example, is considered the “gambling Mecca” (even though gambling is strictly prohibited by Islamic law). Many Muslims find these out-of-context uses offensive.
In an effort to distinguish between the metaphorical and official references to the holy site, the Saudi Arabian government began promoting a new transliteration, Makkah al-Mukkaramah, in the 1980s. Many English-speaking Muslims now consider this the preferred spelling, and closer to the original Arabic. While this new usage has been officially adopted by the U.S. Department of State, its spread is still incipient among anglophones at large.