This is pretty funny mainly because it fits so perfectly into everything we know about Obama already. To Obama, everything is about Obama. (Remember he gave his own speeches to the Queen as a gift last time they met.)
Here, Obama attempts to toast the Queen but something else is going on, the band is playing “God Save the Queen” and everyone is at complete attention for that. But poor Obama thought he just had a soundtrack for his little speech and rambles on while all ignore him completely and then at the very end he realizes nobody’s paying attention to him.