I will concede the point that there are a lot of days and it would be impractical to avoid all of them for elections. However, there is a pretty massive outlier. Most of those countries that were colonies gained independence after WW2 (Iraq and Afghanistan being notable exceptions) due to a strong shift in public sentiment against imperialism. The US on the other hand gained independence 200 years before any of the other countries on that list in a war between colonists and what at the time was one of the most powerful empires in the world. Culturally speaking I'm sure that even if they don't care too much, British citizens are much more aware of the history of American Independence than most of the other countries on the list since it was a much more dramatic affair. I will say Irish independence would likely be more relevant to British citizens and come with a higher level of historical awareness and even emotional attachment.

EDIT: I will add that the US also has massive cultural significance on a global scale. How many people in the UK watch shows, movies, and listen to music from Egypt compared to from the states? If you look at the music charts in the UK they're dominated by American artists.