Being able to know or sing words to an anthem does not diminish the level of support a person can offer their team..........just ask the Amex crowd? what?
He looks to me the sort of chap who'll just nod along, perhaps with his arms folded over his chest in a hardman hip-hop sort of way, one shirt-sleeve rolled up to reveal a Mel Gibson tattoo, some of his speech-bubble thistled out to hide his anti-semitism.
Before he signed for us do you think he knew the words to GOSBTS? Course not! But now I bet he does (well the bit we modified and sing anyway).
If you were about to go and play for any country, it would surely take half hour to learn the anthem (if you spoke the language). Doesn't effect anything. I probably wouldn't sing god save the queen despite being English as not a monacist or religious but would be as proud as anyone to represent my country in anything.