“the g’dolim in England still do it. In addition, they toast the Queen at every simcha”
Not sure which gedolim you mean. I’ve never heard G-D save the Queen played at a yeshivishe/chareidi chasuna in England, nor have I heard the a toast to HM The Queen made. Perhaps at more modern simchas, the equivalent of MO.
Americans are more patriotic and are always busy flying their flags. We in the UK are flying flags this year because of the Diamond Jubilee, but normally its not done as much as in the US.
I assume the OP assumed that as this was a national event, the Anthem should be played. I wonder if the polish anthem would have been played at the knesiyos gedolos before the war.