It was partly made at the end of WW2 as a way of emphasising the connections between the US and the UK, now that the war was ending. It is, amongst other things, a rallying call for both sides to celebrate their similarities, rather than emphasise their differences. (There's a great scene in the Court towards the end where the differences in culture and history are shown... but it has to be seen, rather than me tell you.)
It was the first film to have a Royal Command performance.
I've always thought of it, like The Red Shoes, as a Xmas movie, for some unknown reason. There's no knowingly obvious Xmas references, and yet it has become a movie for me to watch at this time of year.
It's witty, it's romantic (not something I'm usually too bothered about!), it's funny - and looks great in this restoration.