In Great Britain, they toss letters to the fire so that Father Christmas can receive them directly, whereas in America they post them (they send them by mail).

Unlike in America, where stockings are placed by the fireplace, in Great Britain, stockings are placed next to your bed, so Santa must enter your room to leave you small presents. 

In Great Britain, people leave brandy and a mince pie for Father Christmas because he is a grown-up. In America, though, people leave milk and cookies. 

In Great Britain, people eat roast turkey surrounded by bacon-wrapped cipollatas. The turkey is served with roast potatoes and veggies, usually brussel sprouts. They eat it all with gravy and bread sauce. For dessert, they usually have Christmas pudding, a pudding soaked in alcohol.

In America, they eat roast turkey but it is not served with brussel sprouts or bacon-wrapped sausages. For dessert, however, they eat pecan pie and pumpkin pie. 

In Great Britain, people must remove the Christmas tree within the twelve days after Christmas. Otherwise, they'll have bad luck for the rest of the year. In America, nonetheless, there isn't a fixed date to remove the Christmas tree, so it may wither and stand there until the fourth of July.