Hi Ron: The reason Miya would take offense is that people from the southern states in the US refer to people from the northern states as Yankees. People from the south DO NOT like to be called Yankees, nor do people from Texas. The history goes back to the civil war, when the northerners were called Yankees, and the southerners were called Rebels.
Whether a word is offensive really relates to the cultural context and how it's used. The offensive word for people of African descent in the US has mostly always been used in a deragatory and hateful way. I had never heard the word "Paki" but if it's meant in a deragotory way, then it's not good, even though to someone like me, it just looks like a shortened version of "Pakistani." I don't take offense to "Yank" when someone means "a person from the USA" but it can also have a deragatory context.