this is the dope re: title. MM does not technically have a title Harry has one and she shares in it as his wife. At a divorce she loses title but can use “Duchess of Sussex” as her surname. Meghan Duchess of Sussex is her name. Just as you would be Mrs. Jane Doe if you divorced Mr. John Doe but no longer Mrs. John Doe. But she has no title. Harrys 2nd wife would share the title not an ex wife. But of course the US would ignore all that which is what Markle counts on.

Your last line there is key: “the US would ignore all that.” 

Exactly. 

Asking Americans to care about the difference between Meghan, The Duchess of Sussex, and Meghan, Duchess of Sussex, is pointless. They’re not going to care because the important word of distinction to Americans is “duchess.” Americans are not going to care whether or not a definite article is placed before the word “duchess.” The fact that someone is using the word “duchess” in relation to someone is what is worthy of note.

No one in the US is going to stop Megsy going around calling herself Meghan, Duchess of Sussex. That girl will use it until she dies.