A white person wearing cornrows: Not necessarily cultural appropriation.
Etc
The issue with braids/hairstyles kind of bugs me. Corn rows and/or boxer braids have recently been a hot topic with accusations of cultural appropriation because Kim K recently wore the style and they grew in popularity. White girls who wear the braids shouldn't have to be nervous about whether they're appropriating culture in braiding their hair. Renaissance Faires have hair braiding booths with elaborate braids because braids have been around for all cultures for such a long time. The same type of braid is also known as a Dutch braid. Just because women are wearing these to music festivals now or because a celebrity made them popular, suddenly it's cultural appropriation.
I knew a Jewish woman who would always wear gorgeous scarfs over her hair on certain days because she couldn't show her hair due to her religion. I had no idea this is why she did it at the time; I loved the style, and wore a scarf too one day. She complimented me on it and I said, "I saw you rock it so decided to try it too." She said "oh I do it because I have to due to my religion haha."
Is that cultural appropriation? Probably not. If a celebrity did it though and it caught on in popularity, I feel like it suddenly would be though, and that's what bugs. It comes from a place of admiration of the culture.