What are the problems of child marriage like a girl of 13 and getting married with a man of 32

Well, a 13 year old is a minor and a 32 year old is a full grown adult. So, that being said, this is considered illegal in America. But, it is considered a forced-marriage because minors 'can't make their own decisions' so, it is actually considered sexual harassment if they kissed. Unless this is in a different country (other than America)