Yeah, I just remembered being surprised by the (small) size of Russia’s GDP when I looked it up a while back.

Re the Euro, yep, we do have an exception, although I don’t think we’re the only EU country without the Euro (Sweden off the top of my head, maybe Poland too?). I am not really on top of all the macroeconomic implications - I would guess that the Danish krone is probably tied to the Euro at some level, and much of our financial policy is probably tied to EU policy. Could be there are some financial policy options that Denmark has more control over, when opting out of the Euro, but nothing that I am particularly aware of.

I think at a personal level, I would be fine with taking the Euro in Denmark. Easier for travel and online shopping without exchange costs. But that is an uninformed personal view :) I do not have a current detailed understanding of any other implications this would come with for the country - I am just not personally precious about our currency as some kind of national identity symbol.

I think you are right that the Euro would be a core part of any potential UK re-entry negotiations with the EU though.

Russia would not be the largest European economy, even if you counted them. They are about the size of Italy in terms of GDP I believe (not intending this as a correction, just sharing an interesting fact).

Totally agree with your main point, that the UK would be better off pursuing closer ties with Europe and the EU over US.