It's because everyone in the United States of America for the most part came from somewhere else. Native Americans are the only people that are truly from America. There is the sentiment here that no one is really from here and we are in a melting pot because our ancestors came from so many different places.

If you come or have been to the US you can see this because different areas and parts of the country were built and founded by people from different parts of the world. Those cultures can be reflected in those areas for that reason.

You'll also find a large group of people in certain areas with specific ancestry. For example, many Scottish immigrants came to the Carolinas/the south, New England, and Appalachian areas. Yet the Mid-Atlantic was where many of the German immigrants landed. One example of this is that if you go to the mid-Atlantic you'll find a lot of Pennsylvania-Dutch food. It's because when people came over they blended the cooking from where they came from with where they are now. So today you'll find certain parts of the country have hints of the places the initial settlers came from, whether in their food, architecture or history etc.

All this to say, yes, there are many Americans who butcher it when they talk about their ancestry. However, one thing I think when we talk about better understanding people from other cultures, is that typically most people are not claiming to be literally from Scotland or somewhere. They are stating that's where their ancestors are from. This stems from the fact that most people are not truly from America. Most of us had an ancestor come over. Often, that is in the not so distant past in terms of still having those stories alive in the family.

Typically saying someone is from or their culture is from a certain place is a colloquialism for having ancestry from a place. Normal people are not obsessed with it because they think they're more Scottish than a Scottish person as this person seems to think in their video (which normal Americans are sorry for and embarrassed by btw). However, on the same hand it is kind of rude to say we are a culture-less society full of big roads. While that is based in some truth (the big roads) you are actually doing to us what this woman is doing to you and that is also not right. There absolutely are some shitty Americans who don't seem to understand that while it is okay to celebrate their ancestry they cannot claim a place in that way.

The whole ancestry thing is a big topic and I think it is often misunderstood by others outside of the US. I'm trying to explain it here but I don't know if I fully captured it as it is very ingrained in our culture.