When it comes to British dialects, most Americans never hear much beyond the BBC English.
My first reaction was that the videos sounded like a foreign language, especially the second one. I had to listen a few times and look up some slang to get most of the meaning, but even then a lot of the Scottish video is not clear.
Hilarious. I caught like every fifth word. Where did this come from?
Run them with CC turned on.
They still don’t make sense. 
Here is the Scottish sketch with subtitles translated into American English:
They came from British television and are available on the internet.
I travelled to London on business and had a hard time understanding the taxi driver. I was looking up videos in Cockney before I visited again. Real Cockneys don’t sound like Dick Van Dyke in Mary Poppins, but if the movie had been realistic most of the audience would have no idea what he was saying.
I suspect that many people from the UK would have problems understanding the videos unless they are familiar with the local dialects. This skit from the movie, Airplane, is similar for Americans:
An interesting challenge is to see how far back you can understand the reconstructed language of London, England from the 1300s until today. My observation is that the newer accents are not Cockney but closer to the BBC English:
Cockney and Scotch accents are easy.
Try Geordie
I took a cruise from Southampton and almost everyone was from various parts of the UK. I frequently mistook conversations between people in their local dialects as being in a foreign language.
I never ran into that problem in Ireland. The only British dialect other than BBC English that I found easy to follow is the West Country:
Arthur C. Clarke came from the West Country and I always thought he was from the US or Canada:
I was surprised that people didn’t immediately recognize that I was from the US. I guess they just thought I was speaking with a toned-down West Country or Irish accent.
