Age of Nations

Hi

The discourse around the USA reaching a milestone has caused me to look at this list

https://en.wikipedia.org/wiki/List_of_modern_sovereign_states_by_date_of_formation

And im confused. 1801 certainly is a key date for the UK, but so is 1706. So is 1066 for that matter. And 1922. I cant really find a reason 1801 is the listed date that also makes sense with Germany being 1867 instead of 1991.

Any help greatly appreciated.