Not just so that you don't lose it in case of an invasion, but it is proof that you would be willing to help out the host country in the case they were invaded. Also, that you would not invade them.

In the olden days, the local lords would marry their children together, to create familial groups and ensure that for the forseeable future the local areas would not have a conflict. Modern democracies don't have such valuable family members, we use valuable objects instead.

Just to be a pedant, 18.5 % in the US and same in Canada so 37%.

I wouldn't call that almost half, it used to be about half before the move (NY at 31.3, 19.7 in Canada).

London is still the financial hub in the Europe

yea but that's clear from the context

we use "going to Europe" and "going to the continent" fully aware that the UK is in Europe

I don't think that's a problem, and it doesn't mean that Britain is not in Europe, IMO. Comes naturally with human perspective. "Where did you go this summer?" A) "I stayed in England"; B) "I travelled around Britain"; C) "I went to Europe". All perfectly understandable, I think..

We are nothing, if not needlessly complex!

In the San Francisco Bay Area, the locals refer to SF proper as “The City” (not “Frisco”.)

So, they may live in Cupertino, Palo Alto, or Oakland, but when they say “we’re going to The City for a concert on Saturday!” we can hear them pronounce those capital letters as an unambiguous reference to the one, true City.