This is a common misconception in the United States because many American Mormons are from Utah, located in a region of the country that is predominantly Caucasian. For example, notice on the maps below that Utah and neighboring “non-Mormon” states don’t have substantial African-American populations.
That having been said, there are many black Mormons even in the United States. My wife is one of them! In her years of church membership she has never experienced exclusion or racism. Globally, Caucasians comprise a minority of Church membership and are “losing ground” with each passing year. See my Diversity Slide Show for more. (