The reality of the matter is all cultures (muslim and non-Muslim) have historically accepted this practice. Just a hundred years ago, it was a common practice in the U.S. to marry a young girl off to a man a lot older than her. Hence, today many Muslim and non-Muslim cultures (having not adapted and/or caught up to the western culture) still feel it is ok to do this. This is why you find that 50% of girls are marrying before the age of 18 in India which is a majority Hindu country with minority of Muslims. Similarly, you have certain non-Muslim tribes in Africa who still practice this and has been considered permissible in the jewish religion as well.
The figures below are the percentages of girls married under the age of 18 in majority non-Muslim countries:
Nepal (56%), Central African Republic (57%), Mozambique (55%), Uganda (54%) and others.
The issue of child brides has also reached other countries such as England and the United States where secret illegal weddings are being performed. The awareness of early forced marriage and sexual abuse of young girls in the United States was increased by the April 2008 rescue of numerous children living on a ranch owned by a polygamist sect in Texas.