Meghan is the Duchess of Sussex, since you mentioned her title. Harry is the Duke of same.
I don’t know if it is “explained” so much, but it is certainly explored, and even displayed in this thread:
Note that the hate got the thread closed and one poster warned for racism.
If I can summarize… She’s American, she has a skin color that isn’t pale enough for some, and she apparently was rude to some people at one point though I haven’t seen any actual specifics and that might be rumor to cover up the jingoism/racism.