In my experience, it seems that athletes singing for the national anthem befor sporting events is more of a European thing — especially for those countries that have majestic national anthems. Check out any video clip of Wales when they are hosting an international rugby or soccer game if you want to see an awesome national anthem on display.
Most places they only play the national anthems is international games.
The US is kind of unusual for playing it before EVERY GAME.
Perhaps but in this tournament they teams from all over world, I’ve watched Jamaica, Columbia, Morocco, Panama, Haiti and Zambia all acting the same way