Red underlines on romanized words on Microsoft Word

I was doing a spell check on the Microsoft Word document set to English (United States) and found out there are more errors related to the romanization of words other than English. For example, I put special characters related to how the Romanization of Korean, Japanese, and Chinese words looked like, but it still gives them a red underline for some. This also happened when I put Taodong River (Taodong was spelled incorrectly by Word), which came from the Korean word 대동강. Other words that were correct, and have different versions of the word are "pansori" and "p'ansori," but the one with the apostrophe is marked with a red underline. Also affected was the Shanghai Hongkou District, where the district name was marked in red underlined, derived from 虹口. I know that using English (US) and set to automatically detect another language does not work on writing two languages in one paragraph, I kept getting spelling errors for words other than English with "no reference information" on some of the words provided for substitution of the spell check.