Admittedly I didn’t watched the video (three hours is a bit too much of a demand on my time ATM ) but here in the UK Americans claiming they are Scottish or Irish (or Welsh or British for that matter) are scorned and the butt of many a joke.
It seems to come from
A. The vast majority have extremely tenuous links to the country
B. Those links, if they do exist, were literal generations ago. This would be fine if…
C. They intended to explore said links in any way that’s deeper than “I drank a Guinness.”
From what I am gather after 10 years of living in the UK is that there is a huge amount of resentment towards Americans (and I’m talking in generalities here) as they appear to force their culture on the world via their movies, TV shows, and other media only to then come to a relatively small country and try to claim that county’s culture as their own without even really understanding it or it’s history.
Scotland and Ireland are very proud countries. Both have fought damn hard for their identity, arguably more than America has had to historically, and there are families who date back to the Troubles and the potato famin and even earlier. Their culture, stories, beliefs existed long before colonial America was even established.
Personally, I can understand the resentment. They feel their culture is being co-opted for the sake of clout or a hashtag. There’s no true love or understanding of the Scottish/ Irish/Welsh etc culture from many of the Americans who claim to be so (note I said “most”). Claiming a culture as your own when you don’t really understand it and don’t live in the country is somewhat offensive.
It should be noted that it’s not exclusively Americans who do this, but they certainly are the largest and loudest group.
As an aside, England has a chain of pubs called “Outback” that are supposed to be Australian themed. I went to one once and the most Australian thing about it was you could order Vegemite on toast. All they had done was thrown a surfboard and a few Fosters signs (hardly anyone in Australia drinks Fosters) on the wall and called it a day. My wife and I had one drink and then I told her I wanted to leave as a staff member cosplaying Steve Irwin came out carrying an inflatable crocodile. It was pretty offensive.