How do you feel about singing other countries' national anthems?

Rule Britannia is not the British national anthem.

As for the OP’s question, i don’t really like singing the national anthem of my own country, or of any other. I tend to see them as fairly pointless displays of unreflective nationalism. If other people want to stand and sing, then good luck to them, but i’m not interested in joining in.

Rule, Britannia is not technically an anthem, thought it (or The New Jerusalem) really ought to be. God Save The Queen/King is by far the worst anthem there is.